Alison Erlene Viegas

In the field of semiconductor manufacturing, the advancement and optimization of materials used for decoupling capacitors are crucial for enhancing device performance and reliability. This study provides a detailed comparative analysis of two generations of metalorganic hafnium precursors used in atomic layer deposition (ALD) of high-k dielectrics, specifically focusing on their application in Metal-Insulator-Metal (MIM) decoupling capacitors. The precursors in question are the first-generation Tetrakis(ethylmethylamido)hafnium (TEMAHf) and the third-generation AirLiquide Kahe. Initially, the study, based on previous research with Kahe [1], involved a comprehensive assessment of the new third-generation precursor Kahe, to evaluate its behavior under various ALD conditions. Parameters such as bubbler temperature (T_B), purge time (t_P), precursor pulse time (t_Kahe), ozone exposure time (t_O3), chamber pressure, and deposition temperature (T_D) were experimented. The optimal bubbler temperature was found to be 110°C. It was determined that the best purge option was a pulse time of 20s, as extending the purge time beyond 30s significantly decreased the deposition rate. The optimal Kahe pulse time was found to be 4s. Interestingly, a longer ozone exposure time of 4s was the best option as it reduced the deposition rate while improving thickness non-uniformity. Lowering the chamber pressure improved uniformity but at the cost of a reduced deposition rate. The deposition temperature was evaluated up to 450°C (upper BEoL thermal budget), with an optimal balance between non-uniformity and carbon impurities achieved at 350°C. In all instances, the growth per cycle demonstrated a linear trend, confirming that Kahe deposition at such elevated temperatures has not yet reached the saturation point of the ALD window. Following the characterization of the ALD process, MIM capacitors were fabricated using HfO₂/Al₂O₃/HfO₂ (HAH) dielectrics. Al₂O₃ was specifically chosen to maintain the devices in an amorphous state during deposition, thereby reducing leakage current while achieving better field linearity and reliability. The deposition temperatures were set at 313°C for TEMAHf and 350°C and 400°C for Kahe, with Tri-methyl-aluminum used as the aluminum precursor. Compared to TEMAHf, Kahe provides a more uniform deposition across the 300mm wafers; notably, the deviation decreases as the deposition temperature increases. Both TEMAHf-based and Kahe-based HAH samples remain amorphous during deposition. The comparative analysis covered several key electrical characteristics of MIM capacitors, such as capacitance density, field linearity (α), leakage current behavior, and dielectric breakdown. These properties are essential for determining the suitability of the dielectrics for decoupling applications, where stable capacitance and low leakage currents are paramount. In terms of capacitance density, Kahe provides a more stable performance across applied frequencies, showing less dispersion and maintaining levels up for almost four orders of frequency. Field linearity is smoother with Kahe over frequency, displaying 200 ppm/(MV/cm)² lower values than TEMAHf at low frequencies. Remarkably low leakage currents were observed at operating field conditions of up to 1.5 MV/cm. Leakage-current density curves between TEMAHf-based and Kahe-based MIM at T_D=350°C are quite similar across all applied temperatures (T_M=25-125°C), including similar breakdown points, with a slight improvement for Kahe at T_D=350°C. However, Kahe at T_D=400°C shows a dielectric breakdown nearly 2MV/cm lower, likely due to higher carbon impurities increasing defects and causing earlier breakdowns. Moreover, the electrical reliability of the capacitors was investigated in terms of time-dependent-dielectric-breakdown (TDDB) to ensure long-term performance stability under various external conditions, which is particularly important for applications in environments where capacitors are subjected to fluctuating temperatures and voltages. Kahe-based HAH at T_D=350°C has a better slope and therefore extrapolation behavior even with the most conservative extrapolation models applied, at the highest applicable temperature of 125°C. Thus, Kahe samples meet the industrial standard of a 10-year lifetime under operating conditions at 125°C, fulfilling automotive standards that require such performance [2]. This significant advantage highlights Kahe's superiority in meeting demanding industrial standards for reliability purposes. In conclusion, this comparative analysis not only emphasizes the advancements in precursor chemistry for ALD of high-k dielectrics but also highlights the critical role of optimized deposition parameters in achieving desired electrical properties for decoupling capacitors. The insights gained from this study are expected to guide future developments in capacitor technology, contributing to the enhancement of overall device performance and reliability in semiconductor applications. References: [1] Viegas et al., Incipient Ferroelectric Properties in as-deposited Hafnium Zirconium Oxide for BEOL Applications, AVS 24^th International Conference on ALD, 2024, Helsinki, Finland [2] AEC-Q100, Rev. J, 2023, USA Figure 1

Herein, a systematic study of aluminum‐doped hafnium oxide to utilize its antiferroelectric‐like (AFE) properties for energy storage applications is done. The doping concentration of aluminum is optimized to obtain the AFE‐like phase. In addition, the impact of the postmetallization annealing temperature on the energy storage properties of the materials is studied. Metal–insulator–metal capacitors are fabricated by varying the doping concentration of the Al in HfO₂ from 1.9 to 6.2 at% with a constant thickness of 10 nm by atomic layer deposition. The devices are rapid thermal annealed by varying the annealing temperature from 650 to 800 °C for 20 s. Polarization measurements indicate a clear phase transformation from ferroelectric (FE) to AFE to paraelectric phase with the increase of doping concentration in the polarization measurements. The planar antiferroelectric devices have an energy storage density of 30 J cm⁻³ with 76% efficiency after 10⁵ cycles. The storage density can be further increased by a factor of 16.5 using area‐enhanced substrates to 500 J cm^{− 3} at 73% efficiency. The endurance characteristics are studied for both planar and 3D capacitors which are found to be stable up to 10⁸cycles.

The measurement of acetone in human breath, a known biomarker for diabetes, can act as an effective screening method for diabetes. While gas chromatography and mass spectroscopy based methods can detect gases in low concentration, they are costly, bulky, need complex sample preparation and are slow. Solid state devices such as Field Effect Transistors (FETs) can perform this faster and at a lower cost. In this work, we present the results of acetone gas sensing by molybdenum disulfide (MoS2) based FETs. MoS2 channel was functionalized with polymethyl methacrylate (PMMA). When acetone molecules bind to PMMA, an electrostatic gating effect takes place and changes the electrical characteristics of the FET. More the number of acetone molecules that bind to the PMMA layer, the higher the shift in the drain current-voltage (Id-Vg) curve of the FET. This shift is modeled as a change in the threshold voltage of the FET. The Id-Vg curve was observed to shift downwards, as the acetone concentration increases. The limit of detection was observed to be 0.4 parts per million (ppm). This is the first sub-ppm concentration acetone detection at room temperature using a solid state device.