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A Novel Floating Trap NVSM

IP.com Disclosure Number: IPCOM000009924D
Original Publication Date: 2002-Sep-27
Included in the Prior Art Database: 2002-Sep-27
Document File: 3 page(s) / 43K

Publishing Venue

Motorola

Related People

Bunmi Adetutu: AUTHOR [+3]

Abstract

High voltage requirement of conventional Nonvolatile Semiconductor Memory (NVSM) create a reliability issue, as it exceeds the voltage limits of the scaled peripheral CMOS devices. In this article, we describe a novel floating trap NVSM, which replaces the nitride storage layer with hafnium metal oxide, hence lowering NVSM programming voltage and improving retention reliability.

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A Novel Floating Trap NVSM

Bunmi Adetutu, Jiankang Bu, Hsing Tseng

Abstract – High voltage requirement of conventional Nonvolatile Semiconductor Memory (NVSM) create a reliability issue, as it exceeds the voltage limits of the scaled peripheral CMOS devices. In this article, we describe a novel floating trap NVSM, which replaces the nitride storage layer with hafnium metal oxide, hence lowering NVSM programming voltage and improving retention reliability.

1.      Problems of Conventional Floating Trap NVSM

The floating trap NVSM stores charge in spatially isolated deep level traps in nitride, such as SONOS. Comparing with conventional Flash memory, which stores charge in the polysilicon as free carriers with a continuous spatial distribution, SONOS allows the further scaling of tunnel oxide, thus decreases the programming voltage to some extent. However, Coulombic repulsion for high density stored charge and thermal excitation at high temperature degrades retention reliability. Effort to deepen the trap level or decrease trap density by replacing nitride with oxynitride in turn increases the programming voltage.

2.  Proposed Solution

As MOSFET dimensions are scaled, the gate leakage current becomes unacceptably high when the gate oxide is scaled to a thickness range where direct tunneling is the primary conduction mechanism. To further scale CMOS, a major thrust is to replace SiO2 with a thicker dielectric that has higher permittivity, i.e. high K metal oxide. [1] For NVSM, the program speed is more sensitive to potential barrier / programming voltage, and the retention depends more on the tunneling distance (tunnel oxid...