Optimization of Urea-EnFET Based on Ta2O5 Layer with Post Annealing

Lue, Cheng-En; Yu, Ting-Chun; Yang, Chia−Ming; Pijanowska, Dorota G.; Lai, Chao−Sung

doi:10.3390/s110504562

Cited by 36 publications

(24 citation statements)

References 25 publications

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“…The current sensitivity per pH for the literature work was extracted using Eq. (9) Kim et al [22] Gao et al [23] Tarasov et al [25] Rigante et al [26] Zafar et al [27] Sarkar et al [28] Lue et al [29] This work…”

Section: Sensitivity Modelmentioning

confidence: 94%

Effect of subthreshold slope on the sensitivity of nanoribbon sensors

Zeimpekis¹,

Hu²,

Ditshego³

et al. 2016

Nanotechnology

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Abstract. In this work, we investigate how the sensitivity of a nanowire or nanoribbon sensor is influenced by the subthreshold slope of the sensing transistor. Polysilicon nanoribbon sensors are fabricated with a wide range of subthreshold slopes and the sensitivity is characterized using pH measurements. It is shown that there is a strong relationship between the sensitivity and the device subthreshold slope. The sensitivity is characterized using the current sensitivity per pH, which is shown to increase from 1.2%/pH to 33.6%/pH as the subthreshold slope improves from 6.2 V/dec to 0.23 V/dec respectively. We propose a model that relates current sensitivity per pH to the subthreshold slope of the sensing transistor. The model shows that sensitivity is determined only on the subthreshold slope of the sensing transistor and the choice of gate insulator. The model fully explains the values of current sensitivity per pH for the broad range of subthreshold slopes obtained in our fabricated nanoribbon devices. It is also able to explain values of sensitivity reported in the literature, which range from 2.5%/pH to 650%/pH for a variety of nanoribbon and nanowire sensors. Furthermore, it shows that aggressive device scaling is not the key to high sensitivity. For the first time, a figure-of-merit is proposed to compare the performance of nanoscale field effect transistor sensors fabricated using different materials and technologies.

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Section: Sensitivity Modelmentioning

confidence: 94%

Effect of subthreshold slope on the sensitivity of nanoribbon sensors

Zeimpekis¹,

Hu²,

Ditshego³

et al. 2016

Nanotechnology

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“…Several materials have been studied, including SiO 2 , Si 3 N 4 , Al 2 O 3 , SnO 2 , ZrO 2 , and Ta 2 O 5 [17]- [21]. Ta 2 O 5 has proven to be an excellent material with good immunity against interference ions and a wide working pH range [22].…”

Section: Introductionmentioning

confidence: 99%

“…Using only a single ISFET sensor, various enzymes such as urease [22], [23], creatinine deiminase [24], and glucose oxidase [25] have been used to modify the surface of the ISFET gate to be sensitive towards a specific substrate. Nevertheless, enzyme kinetics (i.e.…”

Section: Introductionmentioning

confidence: 99%

An Integrated Circuit for Chip-Based Analysis of Enzyme Kinetics and Metabolite Quantification

Cheah

MacDonald

Martin

et al. 2016

IEEE Trans. Biomed. Circuits Syst.

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Abstract-We have created a novel chip-based diagnostic tools based upon quantification of metabolites using enzymes specific for their chemical conversion. Using this device we show for the first time that a solid-state circuit can be used to measure enzyme kinetics and calculate the Michaelis-Menten constant. Substrate concentration dependency of enzyme reaction rates is central to this aim. Ion-sensitive field effect transistors (ISFET) are excellent transducers for biosensing applications that are reliant upon enzyme assays, especially since they can be fabricated using mainstream microelectronics technology to ensure low unit cost, mass-manufacture, scaling to make many sensors and straightforward miniaturisation for use in point-of-care devices. Here, we describe an integrated ISFET array comprising 2 16 sensors. The device was fabricated with a complementary metal oxide semiconductor (CMOS) process. Unlike traditional CMOS ISFET sensors that use the Si 3 N 4 passivation of the foundry for ion detection, the device reported here was processed with a layer of Ta 2 O 5 that increased the detection sensitivity to 45 mV/pH unit at the sensor readout. The drift was reduced to 0.8 mV/hour with a linear pH response between pH 2 -12. A high-speed instrumentation system capable of acquiring nearly 500 fps was developed to stream out the data. The device was then used to measure glucose concentration through the activity of hexokinase in the range of 0.05 mM -231 mM, encompassing glucose's physiological range in blood. Localised and temporal enzyme kinetics of hexokinase was studied in detail. These results present a roadmap towards a viable personal metabolome machine. Index Terms-Biosensor, CMOS, electrochemical sensor, enzyme kinetics, hexokinase, ion-sensitive field effect transistors (ISFET), metabolomics, point-of-care (POC) diagnostics.

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“…Specifically, it is known that heating the as-grown, amorphous ATO to high temperatures around will result in the formation of crystallization oxide. 13,21,22 Phase transformations and reactions in solids are typically accompanied by volume changes that can induce stresses when the material is subjected to a mechanical constraint. In Ta capacitors, this occurs because the ATO dielectric is constrained by the underlying Ta metal.…”

mentioning

confidence: 99%

“…[8][9][10] Heat treatment below the crystallization temperature of ATO is known to improve its electrical properties. [11][12][13][14][15] However, some of the details of the oxide transformation and structural change of ATO during heat treating below its crystallization temperature remain unclear. 14,[16][17][18][19][20] Temperature and atmosphere are the main parameters controlling the oxide transformation.…”

mentioning

confidence: 99%

In-Situ Stress Measurement during Heat Treatment of Amorphous Tantalum Oxide

Viste

Hossick-Schott

et al. 2015

ECS J. Solid State Sci. Technol.

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Heat treatment is known to improve the electrical and mechanical properties of amorphous tantalum oxide (ATO) in tantalum capacitor anodes. In-situ, multi-beam optical stress sensor (MOSS) measurements were performed on the ATO / tantalum system during heat-treatment in air and vacuum. Thermal desorption mass spectroscopy was also used to monitor species desorbing from the oxide during heating in vacuum. In addition, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the heat-treated samples. The results suggest that the ATO/Ta system undergoes changes as a function of annealing temperature and atmosphere. At temperatures below ∼400 • C, the main effects are oxide dehydration and densification, indicated by a net compressive stress. After heat-treatment at temperatures above 400 • C in air, the net stress becomes increasingly compressive with increasing temperature. Oxide growth due to oxygen uptake is the likely cause for the compressive stress. In vacuum, the net stress remains tensile even after heat-treating at high temperatures above 400 • C. Dehydration and the formation of a high density of oxygen vacancies at the metal-oxide interface during heat-treatment are the likely causes for the net tensile stress-thickness. Tantalum capacitors are widely used in various electrical systems.1-3 Amorphous tantalum oxide (ATO) serves as the dielectric. The use of tantalum capacitors in high reliability applications generated intensive research on the electrical properties of the ATO, specifically on phenomena related to dielectric breakdown in high electric fields.3-7 Oxide defects such as interstitial oxygen ions and oxygen vacancies can significantly influence electrical and mechanical properties of ATO. [8][9][10] Heat treatment below the crystallization temperature of ATO is known to improve its electrical properties. 11-15However, some of the details of the oxide transformation and structural change of ATO during heat treating below its crystallization temperature remain unclear.14, [16][17][18][19][20] Temperature and atmosphere are the main parameters controlling the oxide transformation. Specifically, it is known that heating the as-grown, amorphous ATO to high temperatures around will result in the formation of crystallization oxide. 13,21,22 Phase transformations and reactions in solids are typically accompanied by volume changes that can induce stresses when the material is subjected to a mechanical constraint. In Ta capacitors, this occurs because the ATO dielectric is constrained by the underlying Ta metal. In-situ stress measurements have been previously employed to explore the details of phase transformations and reactions in thin solid films. 3,18,[23][24][25] In our recent work, this approach has been used to study the amorphous-to-crystalline phase transition in ATO under high electrical fields.3,26 For example, compressive stress of 0.06 GPa was generated in the ATO along with morphological changes that lead to cracking in the dielectric. 26 In the present stud...

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Optimization of Urea-EnFET Based on Ta2O5 Layer with Post Annealing

Cited by 36 publications

References 25 publications

Effect of subthreshold slope on the sensitivity of nanoribbon sensors

Effect of subthreshold slope on the sensitivity of nanoribbon sensors

An Integrated Circuit for Chip-Based Analysis of Enzyme Kinetics and Metabolite Quantification

In-Situ Stress Measurement during Heat Treatment of Amorphous Tantalum Oxide

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