Nonvolatile Flash Memory Device Using Ge Nanocrystals Embedded in HfAlO High-&amp;lt;tex&amp;gt;$kappa$&amp;lt;/tex&amp;gt;Tunneling and Control Oxides: Device Fabrication and Electrical Performance

Chen, Jing Hao; Wang, Yingqian; Yoo, Won Jong; Yeo, Yee-Chia; Samudra, G.; Chan, D.S.H.; Du, An; Kwong, Dim‐Lee

doi:10.1109/ted.2004.837011

Cited by 98 publications

(33 citation statements)

References 17 publications

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“…HfAlO was chosen as the tunneling and control oxides in the memory structures due to its promising performance for high-k gate dielectric application 23 and floating gate memory device application. 19 Before tunneling HfAlO film deposition, the p-Si͑100͒ substrate with a resistivity of 4 -6 ⍀ cm was first etched by a HF ͑10%͒ solution for 10 s. Then one very thin layer of HfAlO film was deposited on the Si substrate by the laser molecular beam epitaxy ͑MBE͒ technique using a KrF excimer laser ͑LPX 205i, Lambda Physik, 248 nm in wavelength, 30 ns in pulse width, operated at 1 Hz͒. The ratio of Hf to Al for the ceramic target is 1:2.…”

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confidence: 99%

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Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

2006

Applied Physics Letters

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A nonvolatile flash memory device has been fabricated using carbon nanotubes ͑CNTs͒ as a floating gate embedded in HfAlO ͑the atomic ratio of Hf/ Al is 1:2͒ high-k tunneling/control oxides and its memory effect has been observed. Capacitance-voltage ͑C-V͒ measurements illustrated a 400 mV memory window during the double C-V sweep from 3 to −3 V performed at room temperature and 1 MHz. Further studies on their programming characteristics revealed that electron is difficult to be written into the CNTs and the memory effect of the structures is mainly due to the holes traps. The memory window width can remain nearly unchanged even after 10 4 s stressing, indicating excellent long term charge retention characteristics. We therefore suggest that the CNTs embedded in HfAlO can be potentially applied to floating gate flash memory devices. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2179374͔Since their discovery in the early 1990s, 1 carbon nanotubes ͑CNTs͒ have attracted much attention, both of scientific and technological interest, for possible nanoelectronic applications. To date, a number of nanoelectronic devices have been realized with CNTs, such as field effect transistors, 2-4 room-temperature single-electron transistors, 5 logic gate circuits, 6 inverters, 7 and electromechanical switches. 8 Very recently, the prototypes of memory devices based on CNT field effect transistors were also reported, 9-12 demonstrating another significant extension of CNTs applications. From then on, several groups have carried out research on the CNT-based memories. [13][14][15][16][17] In these research works, the CNTs were synthesized on a conductive Si substrate capped by several hundred nanometers of SiO 2 . Metal electrodes were evaporated on the CNTs to form source and drain electrical contact to them. The conductive Si substrate actually acts as the gate of the memory device. The function of the CNTs was the current channel, and the memory effect of the devices was attributed to the charges injected from the CNTs to the defects or charge traps in the dielectrics or the interface between the CNTs and the oxides. 15-17 The CNTs were not used as the charge storage nodes.For commonly studied flash memory devices, Si, 18 Ge, 19 and Si 1−x Ge x ͑Ref. 20͒ nanocrystals are widely used as the charge storage nodes and the memory structures are sandwiched with nanocrystals embedded in the SiO 2 or high-k dielectrics. But up to now, there is no report on flash memory devices using CNTs as a floating gate. In terms of electrical properties, CNTs have many unique advantages for the application in memory devices such as tunable band gap, high thermal stability and chemical inertness, perfect sidewall structure, and nearly zero surface states. 21,22 These unique properties are very favorable for their application as the charge storage nodes in the memory devices. In this letter, we report the fabrication of the HfAlO/ CNTs/ HfAlO/ Si memory structures and characterization of the unique memory characteristics of CNTs using as the c...

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confidence: 99%

“…For commonly studied flash memory devices, Si, 18 Ge, 19 and Si 1−x Ge x ͑Ref. 20͒ nanocrystals are widely used as the charge storage nodes and the memory structures are sandwiched with nanocrystals embedded in the SiO 2 or high-k dielectrics.…”

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confidence: 99%

Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

2006

Applied Physics Letters

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“…Previously, many materials have been investigated for use as the storage node. These include semiconductors (Si [7] and Ge [8]) and metals (Au, Ag, Co, Ni, Pt, and W [3]- [5]). Issues with previous works include low WF, poor area coverage, and low number density of NC.…”

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confidence: 99%

Metal Nanocrystal Memory With Pt Single- and Dual-Layer NC With Low-Leakage $\hbox{Al}_{2}\hbox{O}_{3}$ Blocking Dielectric

Singh

Bisht

Hofmann

et al. 2008

IEEE Electron Device Lett.

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Abstract-In this letter, we report metal nanocrystal (NC)-basedFlash memory devices with single-layer (SL) and dual-layer (DL) Pt NCs as the storage element. The devices are fabricated using CMOS compatible process flow with optimized low-leakage high-k Al 2 O 3 as the control dielectric. Large memory window (10 V for SL and 15 V for DL devices) is observed due to overerase, which increases the overall window. Improvement in DL memory window is found to be due to 1.5 times improvement in total stored charge over SL. Excellent high-temperature precycling retention is observed both for SL and DL devices.Index Terms-Dual layer (DL), flash memory, metal nanocrystal (NC).

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“…Nanocrystal (NC) flash [3]- [12] and charge trap flash (CTF) [13], [14] are considered as possible alternatives. CTF devices reported so far show good memory window but poor retention [13], [14], while the NC devices show poor memory window [4], [6], [11], [12]. Poor retention of CTF is linked to shallow trap depth of the nitride storage layer, which is an inherent material property and is difficult to control [14].…”

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“…Previously reported small memory window of the NC devices can be attributed to nonoptimal NC number density (ND), size distribution, small area coverage (AC), and low NC WF or high control dielectric (CD) leakage. A significant amount of work on NC-based Flash memory structures has focused on semiconductor NCs like Si [3] and Ge [4]. Issues with semiconductor-based NCs are small WF, quantum-confinement (QC)-related WF lowering, and poor control of NC size that result in poor overall performance of such devices.…”

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confidence: 99%

Performance and Reliability of Au and Pt Single-Layer Metal Nanocrystal Flash Memory Under nand (FN/FN) Operation

Singh

Hofmann

Singh

et al. 2009

IEEE Trans. Electron Devices

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Abstract-In this paper, we report on the fabrication and reliability characterization of gold (Au) and platinum (Pt) single-layer nanocrystal (NC)-based Flash memory devices for NAND application. The devices are fabricated using a CMOS-compatible process flow with high-quality (low leakage and large breakdown) Al 2 O 3 as the control dielectric. The impact of processing conditions on the NC size, area coverage, and number density is also investigated. Large memory window (∼7.5 V for Au and ∼10 V for Pt) and good retention are observed for both Au and Pt NC devices. Excellent postcycling retention is also noted for Pt NC devices. Endurance characteristics are found to be of concern as maximum of only 1 × 10 3 and 4 × 10 3 cycles can be obtained for Au and Pt devices, respectively. Anneal-temperature-dependent gate leakage is observed in Au devices and is investigated using analytical methods. Diffusion of Au atoms from the NC into the gate dielectrics is seen which correlates to the electrical measurements. Postcycling retention and program/erase of Pt NC devices are shown to be good.Index Terms-Cycling endurance, Flash memory, memory window, metal nanocrystals (NCs), reliability failure, retention, transmission electron microscopy (TEM)/electron diffraction (EDX).

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Nonvolatile Flash Memory Device Using Ge Nanocrystals Embedded in HfAlO High-<tex>$kappa$</tex>Tunneling and Control Oxides: Device Fabrication and Electrical Performance

Cited by 98 publications

References 17 publications

Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

Metal Nanocrystal Memory With Pt Single- and Dual-Layer NC With Low-Leakage $\hbox{Al}_{2}\hbox{O}_{3}$ Blocking Dielectric

Performance and Reliability of Au and Pt Single-Layer Metal Nanocrystal Flash Memory Under nand (FN/FN) Operation

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