Multi-point failure analysis sample treatment method

Abstract

The invention provides a multi-point failure analysis sample treatment method, which comprises the following steps: S1, providing a semiconductor sample containing a plurality of failure analysis points, the horizontal distance between adjacent failure analysis points being greater than or equal to 200 [mu] m; s2, a to-be-detected target failure analysis point is selected, and a removable viscous protection layer is adopted to cover the area except the target position of the target failure analysis point; s3, performing grinding operation on the target position until a target structure corresponding to the target failure analysis point is exposed; s4, carrying out data acquisition on the exposed target structure; and S5, removing the viscous protection layer, and repeating the steps S2 to S4 on the rest failure analysis points in sequence until data acquisition of all the failure analysis points is completed. According to the method, for failure analysis points with the interval larger than or equal to 200 micrometers, the physical isolation boundary is constructed through the protection layer, mechanical force or ion beam energy is prevented from diffusing to adjacent areas in the grinding process, and the problems that in a large-interval scene, traditional mechanical grinding precision is out of control, and the PFIB range is insufficient are solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for processing samples for multi-point failure analysis. Background Art

[0002] In the field of semiconductor failure analysis, it is often necessary to grind samples to achieve layer-by-layer observation or positioning. In practice, samples often contain multiple failure analysis points, and due to their layout characteristics, it is difficult to process each point individually through separate slicing. At the same time, multiple failure analysis points are often distributed at different levels, resulting in the need for layer removal operations to take into account the inspection requirements of different depths.

[0003] Among existing delamination technologies, PFIB (Xe plasma focused ion beam), as a comprehensive analysis platform combining a high-resolution scanning electron microscope and a gas injection system (GIS), has the ability to delayer large-area samples with high efficiency. Its delayering effect is uniform and accurate. In addition, because it uses inert gas Xe as the ion source, the xenon gas generated after acting on the sample is directly extracted, avoiding the injection contamination problem that may be caused by traditional ion sources. However, this equipment has significant limitations. Its cutting range is only 100um×100um, which has a range limitation problem when facing samples with complex layouts in multiple areas.

[0004] Another commonly used mechanical grinding method, while cost-effective, requires constant adjustment of the force direction or grinding rate. This results in low delamination efficiency, a narrow controllable range, and difficulty in precise precision control. This can easily lead to over-grinding in practice. Furthermore, while discarding some failure locations can maintain surface flatness and reduce the number of failure analysis points required, it can result in incomplete failure analysis data collection and fail to meet the requirements for comprehensive and accurate failure location and analysis. Summary of the Invention

[0005] In order to solve all or part of the problems of the above-mentioned prior art, the present invention provides a multi-point failure analysis sample processing method. For failure analysis points with a spacing of ≥200μm, a physical isolation boundary is constructed through a protective layer to prevent the mechanical force or ion beam energy from diffusing to adjacent areas during the grinding process, thereby solving the problems of uncontrolled precision of traditional mechanical grinding and insufficient PFIB range in large-pitch scenarios.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for processing samples for multi-point failure analysis comprises the following steps:

[0008] S1. Provide a semiconductor sample containing multiple failure analysis points, with the horizontal spacing between adjacent failure analysis points ≥ 200 μm;

[0009] S2. Select the target failure analysis point to be detected and use a removable adhesive protective layer to cover the area other than the target location of the target failure analysis point;

[0010] S3. performing a grinding operation on the target position until the target structure corresponding to the target failure analysis point is exposed;

[0011] S4. collecting data on the exposed target structure;

[0012] S5. Remove the adhesive protective layer and repeat steps S2 to S4 for the remaining failure analysis points until data collection for all failure analysis points is completed.

[0013] A plurality of failure analysis points are distributed on the same plane level of the semiconductor sample.

[0014] The plurality of failure analysis points are distributed at different depth levels of the semiconductor sample, and top layers of the failure analysis points at different depth levels are located at different planes.

[0015] In step S3, the grinding operation adopts mechanical grinding.

[0016] In step S3, the milling operation is performed by ion beam milling, specifically an inert gas ion milling machine.

[0017] In step S3 , the polishing process is observed by an optical microscope and a scanning electron microscope (SEM) to confirm whether the target failure analysis layer is reached.

[0018] In step S4 , the failure analysis data is collected by imaging the exposed failure analysis layer using a scanning electron microscope (SEM), and the analysis data is recorded and stored.

[0019] In step S5, after the sticky protective layer is removed, the sample surface is cleaned with deionized water or an organic solvent such as acetone to remove residual sticky substances.

[0020] The adhesive protective layer is made of one of 3M tape, polyimide tape, polyvinyl alcohol (PVA) tape or silicone tape.

[0021] In step S2, when the target failure analysis point to be detected is located at the edge of the semiconductor sample, the edge of the adhesive protective layer is ≥50 μm away from the failure analysis point. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The present invention provides a flowchart of a method for processing samples for multi-point failure analysis.

[0024] Figure 2 Schematic diagram of multiple failure analysis points distributed on the same plane level of a semiconductor sample according to an embodiment of the present invention.

[0025] Figure 3 FIG. 1 is a schematic diagram showing that multiple failure analysis points are distributed at different depth levels of a semiconductor sample according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] In the embodiment of the present invention, in combination with reference Figures 1 to 3 As shown, a method for processing samples for multi-point failure analysis is provided, comprising the following steps:

[0028] S1. Provide a semiconductor sample containing multiple failure analysis points, with the horizontal spacing between adjacent failure analysis points ≥ 200 μm;

[0029] S2. Select the target failure analysis point to be tested and cover the area except the target location of the target failure analysis point with a removable adhesive protective layer;

[0030] S3. Performing a grinding operation on the target position until the target structure corresponding to the target failure analysis point is exposed;

[0031] S4. Collect data on the exposed target structure;

[0032] S5. Remove the adhesive protective layer and repeat steps S2 to S4 for the remaining failure analysis points until data collection for all failure analysis points is completed.

[0033] Aiming at the layout scenario where the horizontal spacing between adjacent failure analysis points in semiconductor samples is ≥200μm, the present invention innovatively proposes a regional selective protection method based on a removable adhesive protective layer, which effectively solves the bottleneck problem of traditional technology in processing multiple points with large spacing. When the spacing between adjacent failure analysis points is less than 200μm, the existing technology can achieve collaborative grinding and observation through conventional means; when the spacing is ≥200μm, mechanical grinding is prone to over-grinding of the target area and uneven surface due to insufficient force control accuracy, and PFIB is limited to a cutting range of 100μm×100μm, and cannot cover multiple points with a larger span for simultaneous processing. The present invention uses a removable adhesive protective layer to cover the non-target area, exposing only the target position where the single failure analysis point to be processed is located (adjacent points are isolated by the protective layer to form independent operating units), and then performs directional grinding on the target position, exposing the target structure of the corresponding depth layer by layer by controlling the grinding parameters.

[0034] When multiple failure analysis points are distributed on the same plane level of semiconductor samples, such as Figure 2 As shown in the figure, using points 1 and 2 as an example, points 1 and 2 are located on the same layer with a horizontal spacing of ≥200μm. During the polishing operation of the target failure analysis point (e.g., point 1), a sticky protective layer is used to isolate and protect adjacent points. First, the sample surface is calibrated using an optical microscope or a visual positioning system to determine the locations of the target failure analysis point (point 1) and the adjacent failure analysis point (point 2). High-precision laminating equipment or a dispensing process is then used to apply a sticky protective layer to the sample surface, excluding the target area where the target failure analysis point (point 1) is located. The physical isolation of the sticky protective layer divides the target failure analysis point (point 1) and the adjacent failure analysis point (point 2) into independent operational units, preventing the spread of mechanical forces, abrasive particles, or ion beam energy to adjacent areas during polishing, thereby preventing structural damage or contamination of the untreated adjacent failure analysis point (point 2).

[0035] When multiple failure analysis points are distributed at different depth levels of a semiconductor sample, and the top layers of the failure analysis points at different depth levels are at different planes, such as Figure 3 As shown, taking points 3 and 4 as an example, point 3 is located at a high level and point 4 is located at a low level. When executing step S2 to select the target failure analysis point to be tested, it is necessary to first determine whether the grinding operation of the high-level target point (such as point 3) will involve the top layer of the low-level failure analysis point (such as point 4). If it is determined that grinding point 3 will involve the top layer of point 4, a removable adhesive protective layer is used to cover the area where point 4 is located. If it is determined that grinding point 3 will not involve the top layer of point 4, then there is no need to cover point 4 with a adhesive protective layer to improve processing efficiency.

[0036] Specifically, in step S3, the grinding operation can be performed by mechanical grinding or ion beam grinding. When mechanical grinding is used, the target area material is removed layer by layer by precisely adjusting the grinding pressure, grinding rate, and grinding direction. This method is suitable for scenarios that are sensitive to grinding efficiency and cost. When ion beam grinding is used, it is preferred to configure a grinding device with an inert gas ion source (such as Ar / Xe ions). The grinding time is dynamically adjusted according to the depth of the target structure. This method is suitable for scenarios that require higher grinding uniformity and surface accuracy.

[0037] During the grinding process, a collaborative observation mechanism using an optical microscope and a scanning electron microscope (SEM) is employed: First, the macroscopic morphology of the grinding area is observed using an optical microscope (50-200x magnification) to preliminarily determine whether it is close to the approximate location of the target failure analysis layer; then, a scanning electron microscope (resolution ≤5nm) is used for microstructural analysis. By comparing the thickness parameters of the standard process layers (such as dielectric layer thickness, metal layer spacing, etc.) with microscopic image features, the specific layer reached by the actual grinding and the material removal thickness are confirmed until the target structure corresponding to the target failure analysis point is fully exposed. This dual observation mechanism achieves closed-loop control of the grinding process from macroscopic positioning to microscopic confirmation, effectively avoiding the insufficient accuracy of traditional single observation methods.

[0038] In step S4, the failure analysis data collection specifically includes: using a scanning electron microscope (SEM) to perform high-resolution imaging of the exposed failure analysis layer to obtain the microscopic morphological characteristics of the target structure (such as surface defects, structural anomalies, interface bonding state, etc.); synchronously combining an energy dispersive X-ray spectrometer (EDS) to perform component analysis on the target area, detect element composition and distribution, and identify whether there is foreign matter contamination, element segregation or interlayer diffusion anomalies; for analysis points involving electrical performance failure, DC or high-frequency test signals are loaded through the probe station to collect electrical parameters such as the volt-ampere characteristics, contact resistance, and insulation withstand voltage of the target structure. The above multi-dimensional detection data is recorded in real time by a dedicated software system, automatically associating the sample coordinate system with the detection point information, and storing it in a database according to a preset format to form a complete analysis data set containing morphological images, component spectra, and electrical performance curves, providing a quantitative basis for subsequent failure mechanism modeling and root cause analysis.

[0039] In step S5, after the sticky protective layer is removed, the sample surface needs to be cleaned for residues: first, use deionized water to preliminarily rinse the area covered by the protective layer to remove surface dust and water-soluble residues; for stubborn residues of sticky substances, select an appropriate cleaning reagent according to the characteristics of the protective layer material, such as anhydrous ethanol, acetone or a special semiconductor-grade cleaner, and remove organic glue residues by wiping with a cotton swab or ultrasonic cleaning. During the cleaning process, the amount of reagents and the action time need to be controlled to avoid chemical damage or ion contamination to the target structure exposed on the sample surface. After cleaning, use high-purity nitrogen to blow dry the sample surface to ensure that there is no liquid residue, providing a clean operating base for the subsequent processing of failure analysis points.

[0040] In step S2, when the target failure analysis point to be detected is located at the edge of the semiconductor sample (i.e., an area ≤50μm away from any outer boundary of the sample), the edge of the adhesive protective layer needs to maintain a safe distance of ≥50μm from the target failure analysis point. For special treatment of the edge area, distance control can effectively avoid the risk of protective layer falling off or edge cracking during the grinding process due to stress concentration at the edge of the sample, while reserving sufficient mechanical force buffer space for the grinding operation in the edge area to prevent the grinding tool from vibrating or causing sudden pressure changes due to contact with the outer boundary of the sample, thereby ensuring that the grinding accuracy of the edge area where the target failure analysis point is located is consistent with that of the non-edge area. This edge protection strategy complements the protective layer covering method of the middle area to jointly construct a selective protection system suitable for failure analysis points in the entire area. The adhesive protective layer can specifically adopt one of 3M tape, polyimide tape, polyvinyl alcohol (PVA) tape, and silicone tape to adapt to different application scenarios.

[0041] The present invention physically isolates non-target failure analysis points through a removable adhesive protective layer. For large-pitch points with adjacent horizontal spacing ≥200μm, they are converted into independent operating units, effectively preventing force diffusion, particle contamination, and energy overflow in ion beam grinding during mechanical grinding, avoiding cross-damage problems such as adjacent structural collapse caused by excessive spacing and limited cross-point processing caused by insufficient PFIB range in traditional technologies. At the same time, there is no need to rely on high-cost equipment such as PFIB. Efficient processing of multiple points can be achieved only with conventional grinding tools and reusable protective layer materials, significantly reducing analysis costs and improving operational flexibility. This ensures that each failure analysis point maintains structural integrity during the grinding and testing process, providing a reliable solution for full-point complete data collection and precise failure location of complex semiconductor samples.

[0042] It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for processing samples for multi-point failure analysis, characterized in that: The following steps are involved: S1. Provide a semiconductor sample containing multiple failure analysis points, with the horizontal spacing between adjacent failure analysis points ≥ 200 μm; S2. Select the target failure analysis point to be detected and use a removable adhesive protective layer to cover the area other than the target location of the target failure analysis point; S3. performing a grinding operation on the target position until the target structure corresponding to the target failure analysis point is exposed; S4. collecting data on the exposed target structure; S5. Remove the adhesive protective layer and repeat steps S2 to S4 for the remaining failure analysis points until data collection for all failure analysis points is completed.

2. The processing method according to claim 1, characterized in that A plurality of failure analysis points are distributed on the same plane level of the semiconductor sample.

3. The processing method according to claim 1, characterized in that The plurality of failure analysis points are distributed at different depth levels of the semiconductor sample, and top layers of the failure analysis points at different depth levels are located at different planes.

4. The processing method according to claim 1, characterized in that In step S3, the grinding operation adopts mechanical grinding.

5. The processing method according to claim 1, characterized in that In step S3, the milling operation is performed by ion beam milling, specifically an inert gas ion milling machine.

6. The processing method according to claim 1, characterized in that In step S3, the polishing process is observed by an optical microscope and a scanning electron microscope to confirm whether the target failure analysis layer is reached.

7. The processing method according to claim 1, characterized in that In step S4, the failure analysis data is collected by imaging the exposed failure analysis layer using a scanning electron microscope, and the analysis data is recorded and stored.

8. The processing method according to claim 1, characterized in that In step S5, after the sticky protective layer is removed, the sample surface is cleaned with deionized water or an organic solvent to remove residual sticky substances.

9. The processing method according to claim 1, characterized in that: The adhesive protective layer is made of one of 3M tape, polyimide tape, polyvinyl alcohol tape or silicone tape.

10. The processing method according to claim 1, characterized in that: In step S2, when the target failure analysis point to be detected is located at the edge of the semiconductor sample, the edge of the adhesive protective layer is ≥50 μm away from the failure analysis point.

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