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Spatially Resolved Local Temperature Mapping with High Accuracy inside a Transmission Electron Microscope

Description:

TECHNOLOGY AREA(S): Materials, Sensors, Electronics 

OBJECTIVE: Develop and validate method/s to measure the local temperature of a specimen of interest while being imaged inside a Transmission Electron Microscope (TEM) to decipher the root cause of defects triggering failure in ICs. 

DESCRIPTION: Characterization of electronic devices via TEM has been an indispensable technique in semiconductor manufacturing. TEM functions through the interaction of electrons with materials resulting in high spatial resolution imaging and spectroscopy of samples under study. To maintain the functionality of DoD microelectronics systems, it is essential to perform a thorough investigation of device failure, which often involves localizing defects on a sub 10 nm scale using TEM. Furthermore, successful semiconductor device fabrication requires systematic reliability testing, which relies on utilizing the TEM in conjunction with analytical techniques to identify the failure mechanism/s associated with malfunctioning electronic devices. In general, TEM allows for the direct observation of materials properties; e.g., defects, which could either impair or improve functionality of samples ranging from electron devices and exotic materials to biological samples. However, electron beam induced damage caused by elastic and/or inelastic scattering of electrons interacting with matter inside the TEM is inevitable. Distinguishing defects caused by the electron beam from the ones intrinsic to the sample under study can be a difficult task; therefore, developing methods to evaluate the root cause of the identified defects in devices is necessary. Electron beam damage can take on any of the following forms [1]: i) Radiolysis or ionization ii) Knock-on or sputtering causing displacement of atoms iii) Heating, which can lead to matter transformation. Though beam damage to the sample is undesirable in most cases, we can utilize it to emulate radiation damage speed-up inside the TEM. Additionally, in-situ TEM studies can be utilized to study the failure mechanisms responsible for malfunctioning and low reliability of semiconductor devices. It is important to measure the sample temperature inside the TEM precisely while imaging as it can influence interpretation and measurement analysis; e.g., determining the lattice constant at room temperature. [2] It is generally difficult to experimentally measure the sample temperature as it depends on various parameters: 1) beam energy, current density and size, 2) sample thickness, and 3) thermal conductivity of the sample. [1, 3-4] Thus, a method integrated with the TEM to measure the sample temperature directly and in real-time is required. Potential methods capable of in-situ sample temperature measurements inside the TEM include [5]: i) bulk plasmon measurement based on electron energy loss spectroscopy (EELS) ii) Raman scattering iii) parallel beam diffraction iv) thermo-reflectance. However, these methods have limitations ranging from sensitive analysis procedure and narrow applicability (i.e., only to specific samples) to low spatial resolution, and therefore do not provide accurate temperature measurement with high spatial resolution (sub 10 nm). Hence, the performer is expected to evaluate, develop and/or integrate methods to measure the sample temperature inside the TEM with high spatial resolution (sub 10 nm) and high accuracy (1°C) to precisely evaluate defects in materials. 

PHASE I: Perform a feasibility study for integrating systems and/or methods with a TEM to allow local temperature mapping and distinguish the effect of electron beam radiation damage from intrinsic material structure of the sample. Specifically, conduct research on techniques of interest to evaluate the feasibility of measuring the sample temperature inside the TEM as described above. The proposed technique should be capable of measuring local sample temperature with high spatial resolution, high accuracy and in real-time. The goal of this technique development is to image the local temperature of the sample of interest inside a TEM quantitatively while adhering to the following constraints: ‒ Spatial resolution: ≤ 10 nm ‒ Temperature sensitivity detection (ΔT): 1 °C ‒ Temporal resolution: Real-time temperature measurement within dwell time If any of the above constraints cannot be met the feasibility report shall include all the rational and relevant research. 

PHASE II: Phase II will result in building, testing and delivering a prototype of the method developed in phase I. Prototype demonstration will include numerous testing data on two main types of experiments in both scanning and parallel TEM operation modes. The first experiment type entails post-mortem analysis of integrated circuits (ICs) to investigate defects. Explicitly, the system will deliver data regarding the influence of beam heating on defect analysis of ICs through quantitative temperature mapping. The second experiment type includes in-situ TEM studies on failure mechanisms of ICs. There is no thermocouple inside TEM to measure the sample temperature and not all TEM sample holders have the capability to measure the approximate sample temperature after the application of external stimuli, which could be heat or electric field or laser. [6] The four main failure mechanisms of ICs include: i) time-dependent dielectric breakdown (TDDB), ii) electromigration (EM), iii) hot carrier injection (HCI) and iv) negative bias temperature instability (NBTI). The performer can select any of the above failure mechanisms to deliver related data pertaining to temperature measurement of the sample of interest. In the second experiment type, the cause of temperature rise of the sample is due to both external stimuli, utilized for studying the failure mechanism, and beam irradiation. 

PHASE III: Phase III will result in the expansion of the prototype system in Phase II into a tested pre-production system, which entails a technique integrated with a TEM for local temperature mapping of samples. This system can be utilized for evaluating failures of ICs both in commercial and government sectors. Additionally, the proposed system enables better understanding of the root cause of defects responsible for failure/s and provides insights regarding various failure mechanisms affecting the functionality and the reliability of semiconductor devices, respectively. Furthermore, the system could have the potential to measure the temperature of samples other than ICs; e.g., biological samples and oxides used for high temperature superconductivity study. 

REFERENCES: 

1: D. B., Williams & C. B., Carter. Transmission Electron Microscopy. New York, NY: Springer Science, 2009.

2:  F. Niekiel, et al., Local Temperature Measurement in TEM by Parallel Beam Electron Diffraction, Ultramicroscopy 176 (2017) 161-169.

3:  R.F. Egerton, et al., Radiation Damage in the TEM and SEM, Micron 35 (2004) 399-409.

4:  D. J. Smith, et al., Exploring Aberration-corrected Electron Microscopy for Compound Semiconductors, Microscopy 62 (2013) S65-S73.

5:  M. Mecklenburg, et al., Nanoscale Temperature Mapping in Operating Microelectronic Devices, Science 346 (2015) 629-632.

6:  S. Hihath, et al., High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy, Scientific Reports 6 (2016), Article number: 23046.

KEYWORDS: TEM, Temperature Mapping, Beam Damage, Failure Analysis, Semiconductor Devices, ICs 

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