Physical Insights on BJT-Based 1T DRAM Cells

The basic operation of BJT-based floating-body 1T DRAM cells on SOI is analyzed with supportive numerical device simulation. Extreme sensitivity of the charging process (write ldquo1rdquo) to the offset (Delta t WB ) between the word-line and bit-line voltage pulses is revealed and explained. The ne...

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Bibliographic Details
Published in:IEEE electron device letters 2009-05, Vol.30 (5), p.565-567
Main Authors: Zhenming Zhou, Fossum, J.G., Zhichao Lu
Format: Article
Language:English
Subjects:
Analytical models
Applied sciences
BJT breakdown voltage
bulk accumulation
Capacitance
capacitorless DRAM
Charge
Charging
CMOS technology
Computer simulation
Depletion
Design. Technologies. Operation analysis. Testing
Detection
Devices
Dynamic random access memory
Electronics
Exact sciences and technology
FinFETs
Gates
Integrated circuits
Integrated circuits by function (including memories and processors)
MOSFET circuits
Numerical simulation
Random access memory
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
SOI floating-body effects
SOI parasitic BJT
Student members
Threshold voltage
Transistors
Writing
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Summary:The basic operation of BJT-based floating-body 1T DRAM cells on SOI is analyzed with supportive numerical device simulation. Extreme sensitivity of the charging process (write ldquo1rdquo) to the offset (Delta t WB ) between the word-line and bit-line voltage pulses is revealed and explained. The necessity of a positive Delta t WB for successful write ldquo1rdquo is related to establishing a high gate capacitance, which is the predominant charge-storage element in the BJT-based cell. Such charging underlies why a fully depleted (FD) cell, e.g., a FinFET, can work for BJT-based DRAM, without an independent bias for accumulation charge that is necessary in conventional FD-MOSFET DRAM cells for charge storage and data sensing. Furthermore, a bulk-accumulation effect in the BJT-based DRAM cell is revealed and described. It undermines the BJT operation and leads to ineffective charging and significant loss of sense margin when the cell body thickness is scaled.
ISSN:0741-3106
1558-0563
DOI:10.1109/LED.2009.2017285