Semiconductor Memory Device Analysis Techniques

Techniques for memory technology analysis

To achieve optimal yield in the shortest possible time, memory analysis tools must deliver high-productivity characterization across a diverse array of memory devices. We have developed essential techniques for accurately measuring critical dimensions of memory devices, alongside sophisticated techniques for fault isolation and defect identification.

Sample preparation of semiconductor memory devices

FIB milling

Cross-sectional or diagonal-focused ion beam (FIB) milling is needed to precisely remove materials in specific locations on DRAM or 3D NAND structures. This application continues to grow, driven by the need for defect analysis, metrology, and characterization of the memory cells themselves, as well as peripheral logic and the complex interconnects within a die or in a package. We offer a range of FIB-SEM solutions that perform milling on a range of length scales, from hundreds of microns down to the nanometer scale. Exceptionally precise and high-quality FIB milling can be performed on individual die using the Thermo Scientific Helios 6 HD FIB-SEM  or the Thermo Scientific Helios 5 PFIB DualBeam or on entire wafers using the Thermo Scientific Helios 5 EXL Wafer DualBeam or the Thermo Scientific Helios 5 PXL PFIB Wafer DualBeam.

TEM sample preparation

TEM sample preparation is a specialized FIB milling technique used to create high-quality, site-specific, thin specimens for TEM imaging, analysis, and metrology. As memory storage cell geometries and control logic structures shrink, there is a greater demand for precise and efficient TEM-based reference metrology and defect root cause analysis data. To meet this growing need, innovations in FIB technology and automated applications have been incorporated into instruments such as the Helios 5 EXL Wafer DualBeam and Helios 6 HD FIB-SEM to support the generation of highly repeatable TEM data on DRAM or 3D NAND devices.

Delayering of semiconductor memory devices

Delayering is a sample preparation process that systematically removes material layer by layer, ensuring high-level planarity and uniformity. This technique is commonly employed in wafer-level defect analysis and die-level sample preparation for nanoprobing on memory devices. We offer advanced solutions such as the Helios 5 PXL PFIB Wafer DualBeam for wafer-level delayering, which automatically prepares planar surfaces at the targeted 3D NAND layers. Additionally, the Helios 5 PFIB DualBeam and Thermo Scientific Helios 5 Hydra PFIB DualBeam are utilized for die-level delayering, enabling the preparation of sample surfaces for nanoprobing. Our proprietary gas chemistry ensures the planarity and uniformity of the delayering process, and we provide automated end-pointing capabilities that allow for precise stopping on any target layer within the memory cell structures.

Fault isolation of semiconductor memory devices

Thermal fault isolation

Memory devices are integrated into different packaging schemes, all of which encounter challenges related to scale, clock speed, heat dissipation, and 3D complexity. Detecting defects in these packaged devices necessitates various techniques, with thermal fault isolation being one of the most common and increasingly relied-upon methods. Through powering up the device and utilizing high- sensitivity thermal optics, failure analysis (FA) engineers can analyze the thermal signature from the package and pinpoint specific areas of interest for further investigation. The Thermo Scientific ELITE System features high-sensitivity optics designed specifically to meet the requirements of memory package FA.

Optical fault isolation

Advanced memory devices possess intricate designs in their peripheral logic circuits, necessitating the application of high-resolution fault localization techniques for effective failure analysis with a high success rate. To address this requirement, the versatile Thermo Scientific Meridian S System offers optical fault isolation capabilities, encompassing laser voltage imaging (LVI), laser voltage probing (LVP), and dynamic laser stimulation (DLS/LADA).

Nanoprobing

SEM-based and AFM-based nanoprobing instruments, such as the Thermo Scientific nProber IV and Hyperion II Systems, are essential for detecting various memory device defects such as wordline to wordline shorts, memory cell faults, and peripheral logic transistor faults. Nanoprobing offers high confidence and precise localization, significantly improving the success rate of subsequent physical failure analysis work. Furthermore, advanced nanoprobing systems like the nProber IV System provide sufficient accuracy and stability to enable detailed electrical characterization of individual transistors, even in the most advanced technology nodes.

Imaging and analysis of semiconductor memory devices

TEM imaging and analysis

TEM is widely employed by memory manufacturers for visualizing and assessing the intricate 3D NAND memory cells, as well as the transistor and capacitor structures, in DRAM. This atomic-resolution data plays a pivotal role in achieving precise control over critical dimensions (CD) that are not readily apparent and in conducting comprehensive defect analysis and characterization. The Thermo Scientific Talos F200E TEM facilitates rapid TEM imaging and defect analysis, bolstered by the support of X-ray energy dispersive spectroscopy (XEDS). With the increasing use of beam-sensitive materials in memory device fabrication, there is a growing demand for high-efficiency TEM imaging and characterization. Addressing this demand, the Thermo Scientific Spectra Ultra (S)TEM is purposefully designed to meet the analytical requirements and enable accurate materials characterization, particularly for beam-sensitive materials like the thin-film stack on DRAM capacitors.

TEM metrology

The current fab metrology solution is inadequate in addressing the challenge posed by the increasing memory cell stacking and the aspect ratio of structures. Memory manufacturers rely on TEM images to conduct atomic-resolution CD measurements, which serve as "gold standard" reference data for other metrology solutions in the fab, such as scatterometry. TEM metrology is extensively utilized for precise CD control in 3D NAND memory cells at every layer, thin film deposition of DRAM capacitors, as well as the underlying wordline and bitline structures. To meet this demanding requirement for high-volume TEM metrology data, the newly developed Thermo Scientific Metrios 6 (S)TEM is specifically tailored for productivity, efficiency, and full automation.

SEM imaging and analysis

SEM imaging and analysis play a crucial role in providing valuable statistical data for memory device fabrication. They are extensively utilized for metrology, defect analysis, and failure analysis within this field. We offer a comprehensive range of products that are designed to deliver high-resolution SEM imaging and analysis capabilities. For instance, the Thermo Scientific Verios 5 XHR SEM is an automated lab SEM that enables large-area imaging on wafer die pieces. Additionally, our DualBeam product portfolio provides SEM imaging along with precision and high-throughput ion beam milling capabilities. This includes the Helios 6 HD FIB-SEM and Helios 5 PFIB DualBeam, and the Helios 5 EXL and Helios 5 PXL PFIB Wafer DualBeams, each offering unique advantages for advanced SEM imaging and analysis requirements.

SEM metrology

SEM metrology uses SEM images for critical dimension measurements over a large area at specific sites. The Thermo Scientific Verios XHR SEM is an innovative solution that provides automated high-resolution SEM imaging specifically designed for memory metrology and analysis on wafer die pieces. Additionally, the Helios 5 PXL PFIB Wafer DualBeam can perform SEM imaging, analysis, and metrology, and it offers the added advantage of combining with focused ion beam cross-sectioning, diagonal milling, and delayering on wafers within the fab, accelerating time to actionable data.

3D TEM and SEM image reconstruction

3D reconstruction involves utilizing SEM or TEM images obtained from a volume of material to create a 3D dataset. Thermo Scientific DualBeam instruments offer a practical solution for this process. Because these DualBeams employ precision milling, the memory device structures can be incrementally removed in thin slices, all while capturing high-resolution SEM images. These images can then be reconstructed using Thermo Scientific Avizo Software, allowing for a comprehensive visualization of the memory device structure. This approach provides valuable insights into the fabrication process and enables a deeper understanding of the device's characteristics.

Electrostatic discharge

Electrostatic discharge compliance

Memory devices are expected to withstand environmental electrostatic discharge (ESD) events throughout their product lifecycle. Designers utilize multiple techniques to protect these sensitive electronic circuits from the damage caused by an unintended ESD event. The industry has standardized methods for qualifying parts against a well-defined set of stress criteria, resulting in classifications that are then assigned to the individual parts. These classifications indicate the maximum stress that the part can experience without any latent or catastrophic failure. The Thermo Scientific MK ESD and Latch-Up Test System and the Thermo Scientific Orion Electrostatic Discharge Tester are the tools of record for ESD event characterization and compliance testing.

For Research Use Only. Not for use in diagnostic procedures.