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Chapter 9.
• Integrated Circuits ( 집적 회로 )– Single Electron Transistor
– Memory
메 모 리 소 자
• Memory Hierarchy
• 양자역학의 세계
• D 램 (DRAM)
• 플래시 메모리 (Flash Memory)
• 플렉시블 메모리 (Flexible Memory)
• 차세대 메모리 소자
Memory Hierarchy
Memory
Random Access Memory (RAM) Read Only Memory (ROM)
Dynamic RAM (DRAM)
Programmable ROM (PROM)
Static RAM (SRAM) Mask ROM
EPROM EEPROM
Flash ReRAM STT-MRAM PoRAM
Volatile Non-volatile
1984 Toshiba
Unknown (next-generation)
PcRAM
Chapter 9: Integrated Circuits
고전 역학과 양자 역학
고전 역학( 축구공이 벽을 통과할 수 없다 )
-
양자 역학( 전자는 벽을 통과할 수 있다 )
나노 크기의 작은 세계
Chapter 9: Integrated Circuits
DRAM 의 기억 원리
-----------
---
+++ + + +
++
정보 저장
정보 유지를 위한 재충전
축전기전자 충전 전원차단 방전 정보 소실
휘발성 메모리
Dynamic RAM
축전기에 전하가 충전된다
Chapter 9: Integrated Circuits
DRAM 소자
DRAM 단면 전자현미경 사진
DRAM 웨이퍼
축전기
트랜지스터
Chapter 9: Integrated Circuits
DRAM 소자
DRAM 모듈
DRAM 패키지
Chapter 9: Integrated Circuits
플래시 메모리의 기억 원리
- - - - -
정보 저장
플로팅게이트전자
`터널링 전원차단 정보유지
비휘발성 메모리
일괄적인 소거
MemoryFlash
Chapter 9: Integrated Circuits
플래시 메모리
플래시 메모리전자현미경 사진
NAND 플래시 메모리NOR 플래시 메모리
플로팅 게이트( 스위치와 축전기 역할을 같이한다 )
Chapter 9: Integrated Circuits
플래시 메모리 제품
플래시 메모리 카드
USB 플래시 메모리
플래시 메모리 SSD
Introduction
유연성을 가지는 메모리
유연성을 가지는메모리 소자
Chapter 9: Integrated Circuits
상용화된 반도체 메모리 소자
2-D CHANNEL
P-Si SUBSTRATE
Source Drain
Capacitor
SiO2
Gate
D-RAM 소자
Cap. 에 데이터를 저장
Flash Memory 소자
2-D CHANNEL
P-Si SUBSTRATE
Source DrainSiO2
Poly SiliconSiO2
Gate
Poly-Si. 에 데이터를 저장
Chapter 9: Integrated Circuits
차세대 메모리 및 반도체 소자
NFGM 소자
2-D CHANNEL
P-Si SUBSTRATE
Source DrainInsulator
GateNano-Crystals
Nano particle 들이 전하를 트랩한다 .
FIN-FET 소자
P-Si SUBSTRATE
Source DrainInsulator
Gate
3 차원적 채널 형성으로 전류특성이 향상 .
Next Generation Single Electron Transistors and
Nonvolatile Flash Memory
• Fabrication and Electrical Properties
End of the Semester
Final-stage image of the fabricated single-electron transistor
End of the Semester
High-electron transmission electron microscopy image of Al nanocrystals formed in the source-drain
channel
End of the Semester
p - Si
ba aorc
Ga+ Beam
AlAl
MgO
Schematic diagram of the nanocrystals formation process in the channel region
End of the Semester
0.0 0.1 0.2 0.3 0.4 0.5
0
4
8
12
16
-40
-20
0
20
40T = 300 K
CO
ND
UC
TAN
CE
( 1
/10- 9
Ω)
DR
AIN
C
UR
REN
T (
nA)
DRAIN VOLTAGE (V)
Drain current and conductance as functions of the drain voltage without applied voltage at room
temperature
End of the Semester
-200 -100 0 100 200
0.38
0.40
0.42
0.44
VDS = 90 mV
VDS = 120 mVT = 300 K
DRAI
N C
URRE
NT (
nA)
DR
AIN
CUR
RENT
(nA
)
GATE VOLTAGE (mV)
0.5
0.6
0.7
0.8
0.9
Drain current as function of the gate voltage at different source voltages
Nonvolatile memory devices based on Nonvolatile memory devices based on nanocompositesnanocomposites
Contents
Formation of inorganic/organic nanocompositesElectrical properties and operating mechanisms of
nonvolatile memory devices based on metal, semiconductor, or core/shell nanoparticles embedded in a polymer layer
Electrical properties and operating mechanisms of
nonvolatile memory devices based on nanoparticles attached
carbon nanotubes embedded in a polymer layer
Advantages of nonvolatile memory devices based on inorganic/organic nanocomposites
Nonvolatile memory device with a cross point structure fabricated by
inorganic/organic nanocomposites
Advantages of inorganic/organic nanocomposites for potential applications in nonvolatile memory devices.
Simple fabrication low cost & high productivity
Ultra-high density Cross point structure
Fast switching time System memory
Flexible memory Mobile devices
Active layers with inorganic/organic nanocomposite
Inorganic/organic nanocomposites
One layer structure Monolayered nanoparticles in a polymer layer Randomly distributed nanoparticles in a polymer layer solution method Spin coating and solvent evaporating Materials Polyimide, PMMA, PVK, MEH-PPV. Metal, Semiconductor, core/shell, CNTs, C60.
Formation of inorganic/organic nanocomposites
Deposition of the bottom electrode on an insulating substrate.
Solving synthesized inorganic nanoparticles embedded in an polymer solution.
Deposition of the solution by spin coating.
Evaporating the solvent in the spin-coated polymer layer.
Deposition of the top electrode on the formed inorganic/organic nanocomposite layer.
Semiconductor nanoparticles
Electrical properties and operating mechanisms of
nonvolatile memory devices based on semiconductor nanoparticles
embedded in a polymer layer
Microstructural properties of ZnO nanoparticles embedded in polyimide nanocomposties sandwiched between two C60 layers
Schematic diagram of the OBD structure
The C60 used in the OBDs an electron transport layer with a very large mobility. The size of ZnO nanoparticles; 4 and 6 nm The surface density of nanoparticles; 2 × 1011 cm−2
The SADP of the ZnO nanoparticles; Hexagonal structure and diffuse rings due to the small particle size
substrateITO
Al
Al
Al
PI
ZnO nanoparticle
C60
C60
Plan-view bright-field TEM image and SADP of the ZnO nanocrytals embedded in a PI layer
Electrical properties of an Al/C60/ZnO nanoparticles embedded in PI/C60/ITO device
I-V curves for an Al/ZnO nanoparticles embedded in PI/ITO devices and Al/C60/ZnO nanoparticles
embedded in PI/C60/ITO device. The ON/OFF ratio for the device with C60 layer; > 104
The ON/OFF ratio for the device without C60 layer; ~ 102
Two orders larger than that for the device without C60 sandwiched layers
The charge injection and the storage capacity in an OBD can be improved by inserting C60 layers.
-10 0 1010-16
10-13
10-10
10-7
10-4
without C60 layer with C60 layer
CURR
ENT
(A)
APPLIED VOLTAGE (V)
state "1"
state "0"
0.1 1 10 1001E-11
1E-9
1E-7
1E-5
CU
RR
ENT
(A)
TIME (h)
"1" state
"0" state
-16 -12 -8 -4 010-12
10-10
10-8
10-6
Verase = 2 V Verase = 3 V Verase = 4 V Verase = 5 V
CURR
ENT
(A)
APPLIED VOLTAGE (V)
Electrical bistability properties and retention characteristics for Al/C60/ZnO nanoparticles embedded in PI layer/C60/ITO device
I-V curves for the device with different erasing voltages from 2 to 5 V.
A gradual discharge process (under various erasing voltages)
Increase of the ON/OFF ratio with increasing Verase
Application in multilevel memory device
I-t curves for device in state 1 under a constant bias of −6 V.
The device remained in the 1 state for several days to weeks without any significant degradation.
The OBDs exhibited excellent retention time at ambient conditions.
Carrier transport mechanisms for an Al/C60/ZnO nanoparticles embedded in PI/C60/ITO device
The electrons injected from the Al electrode are transferred into the C60 layer
Increase in the current of the OBD
Because of the excellent electron affinity of the C60 layer, enhancement of the injection for the electrons from the Al contact into the ZnO/PI hybrid nanocomposite
The improvement of electron capture by the ZnO nanocrystals and enhancement of the memory windows
Schematic diagram of the energy levels for an Al/C60/ZnO nanoparticles embedded in PI
/C60/ITO device.
Vacuum level
ITO C60PI
ZnOPI C60
Al
Microstructural properties of ZnO nanoparticles embedded in a PMMA layer
The size of ZnO nanoparticles is approximately 5 nm.
ZnO QDs were dispersed and attached on the surface of the PMMA.
Schematic diagram of the device
Al/ZnO nanoparticles embedded in a PMMA /ITO device
Plan-view bright-field TEM image of the ZnO nanoparticles embedded in a PMMA layer
Electrical properties of an Al/ZnO nanoparticles embedded in PMMA/ITO device
The I-V result Appearance of clockwise electrical
hysteresis behaviors The maximum ON/OFF ratio; 5 ×
104 at 1 V (1.5 wt% device)
The storage capability is enhanced with increasing concentration of the PMMA molecules
The ON/OFF ratio for 2.5 wt% device is smaller than that for 1.5 wt% device due to the large aggregations of ZnO QDs
The optimized OBD device with a PMMA concentration of 1.5 wt%
I-V curves for the Al/ZnO nanoparticles embedded in PMMA layer/ITO device
-2 -1 0 1 210-12
10-10
10-8
10-6
10-4
OFF
ON
CURR
ENT
(A)
APPLIED VOLTAGE (V)
PMMA 1.5 wt% PMMA 0.5 wt%
Switching results of an Al/ZnO nanoparticles embedded in PMMA/ITO device
The switching results Vwrite; 2 V, Verase; -2 V, Vread; 1 V ON state current; 10-6 A OFF state current; 10-10 A ON/OFF ratio; 104
The difference between the current levels is due to the operation difference between the pulse and the DC.
Al/ZnO nanoparticles embedded in PMMA layer/ITO devices exhibit good switching characteristics of OBDs.
Write-read-erase-read sequence of the Al/ZnO nanoparticles embedded in PMMA/ITO device
Input Voltage Input Voltage
Measured Current Measured Current
Retention measurement of an Al/ZnO nanoparticles embedded in PMMA/ITO device
The retention measurement
The retention ability was tested
under ambient conditions
The applied pulse; 1 V
No significant degradation after 105
cycles of continuous stress was
observed
The experimental results can be
extrapolated to 108 sec (10 years)
The good memory stability of the
OBDs
Currents as functions of the number of cycles for the ON and the OFF states of the Al/ZnO nanoparticles embedded in PMMA/ITO device.
Core/shell nanoparticles
Electrical properties and operating mechanisms of
nonvolatile memory devices based on core/shell nanoparticles
embedded in a polymer layer
Microstructural properties of CdSe:ZnS nanoparticles sandwiched between C60 layers
Schematic diagram of the device structure
The diameters of the CdSe:ZnS nanoparticle; 15 nm The thickness of the ZnS shell; 0.5 nm
GlassITOC60
C60
Al
DC
CdSe
ZnS
Experimental procedure
I-V curves for an Al/C60/CdSe:ZnS nanoparticles /C60/ITO device
The I-V curve An electrical hysteresis behavior An essential feature for a bistable device
The ON/OFF ratio for the device without CdSe:ZnS nanoparticles
Negligible in comparison with that for the device containing CdSe:ZnS nanoparticles
The electrical bistability properties of the OBD can be attributed to the existence of CdSe:ZnS nanoparticles.
Electrical properties of an Al/C60/CdSe:ZnS nanoparticles/C60/ITO devices
-6 -3 0 310-6
10-5
10-4
10-3
10-2
-8 -6 -4 -2 0 2 4 6 810-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
Al / C60 / ITO
Forward ReverseC
UR
REN
T (A
)
APPLIED VOLTAGE (V)
state "1"
Al / C60 / CdSe / C60 / ITO
CU
RR
ENT
(A)
APPLIED VOLTAGE (V)
state "0"
10-1 100 101 102 103
10-5
10-4
10-3
10-2
CURR
ENT
(A)
TIME (h)
state "1"
state "0"
Schematic diagram of the energy band of the Al/C60/CdSe:ZnS nanoparticles/C60/ITO device.
Electrons captured in CdSe core nanocrystals
Generation of the internal electric field by the captured electrons
Decrease in the conductivity of the OBD containing the CdSe:ZnS nanoparticles (low-current 0 state)
Memory mechanism and retention time of Al/C60/ CdSe:ZnS nanoparticles/C60/ITO device
ITO Al
e-
VACUUM
4.8 eV4.3 eV
CdSeZnS
4 eV2.1 eV
3.8 eV
7.1 eV
C60 C60
I-t curves for the Al/C60/CdSe:ZnS nanoparticles/C60/ITO device under 3 V.
The device stayed in the state “1” for several days to weeks, under ambient condition.
The device fabricated in this work exhibited excellent environment stability under ambient conditions.
Nanoparticles attached CNT
Electrical properties and operating mechanisms of
nonvolatile memory devices based on nanoparticles attached carbon nanotube embedded in a polymer
layer
Microstructural properties of ZnO nanoparticles attached MWCNTs
The crystalline ZnO nanoparticles might be formed on defect-like sites of the acid-treated MWCNTs.
HRTEM image of a single ZnO nanoparticle attached on the surface of the MWCNT
Electrical properties of Al/ZnO nanoparticles attached MWCNTs/ITO device
The I-V result
The current hysteresis
The maximum ON/OFF ratio; 104
(ZnO N. P. attached MWCNTs
device)
The I-V result for the device with only
MWCNTs
The electrical bistability of the hybrid
nanocomposite devices is attributed
to the ZnO nanoparticles
I-V curves for the Al/ZnO nanoparticles attached MWCNTs/ITO device
Carrier transport mechanisms of ZnO nanoparticles attached MWCNTs
Schematic diagram of the device
Al/ZnO nanoparticles attached MWCNTs/ITO device
The transported electrons encounter dangling ZnO QDs and transfer to the conduction bands of the ZnO QDs through the covalent bond between the MWCNT and the ZnO QDs.
The conjugation of ZnO QDs on the surfaces of the MWCNTs provides a channel that enhances the electron transfer efficiency
significant increment in the ON/OFF ratio by utilizing ZnO nanoparticles attached MWCNT nanocomposites
Microstructural properties of CdSe:ZnSe nanoparticles attached MWCNTs
(a) HRTEM image of an individual MWCNT after the assembly of 5-nm CdSe/ZnSe nanoparticles, (b) Magnified image of the MWCNT with
linked CdSe/ZnSe nanoparticles.
Side-wall conjugations are clearly observed CdSe/ZnSe nanoparticles are randomly attached on the
surfaces of the MWCNTs
Electrical properties of Al/CdSe:ZnSe nanoparticles attached MWCNTs/ITO device
The I-V result The electrical hysteresis The maximum ON/OFF ratio;
approximately 4 × 104
The I-V result for the device with only MWCNTs
Small ON/OFF ratio The electrical bistability of the
CdSe:ZnSe attached MWCNTs devices is due to the CdSe/ZnSe nanoparticles
The ON/OFF ratio for the surface modification device is two orders larger than that for the device without surface modification
I-V curves for the Al/CdSe:ZnSe nanoparticles attached MWCNTs/ITO device
C60
Electrical properties and operating mechanisms of
nonvolatile memory devices based on C60 embedded in a polymer
layer
The OBD fabricated utilizing C60 embeddedin a PMMA
Al/C60 embedded in PMMA/Al device
Schematic diagram of the device
Electrical properties of an Al/C60 embedded in PMMA/Al device
I-V curves for the device with C60 molecule concentrations of 1, 5, 10, and 25 wt%
The I-V curves Show a current hysteresis behavior the essential feature for a memory
device
The ON/OFF ratios increased with increasing C60 concentration.
maximum ON/OFF ratio; 1.3 x 103 with C60 concentration of 10 wt%
The device without C60 disappears the current hysteresis
The electrical bistability of the OBD is attributed to the existence of C60 molecules
Switching results of an Al/C60 embedded in PMMA/Al device
V-t (input signal) The switching measurement conditions The writing pulse; 5 V (ON state) The erasing pulse; -5 V (OFF state) The reading pulse; 1 V
The duration of each voltage pulse is250 μs with a cycle of 1 ms.
OFF state current; nearly zero ON state current; 20 μA
The number of the pulse cycle is as large as 50,000 times without any deterioration of the performance
The good endurance characteristics of the fabricated device.
I-t (output signal)
Retention results of an Al/C60 embedded in PMMA/Al device
The I-t curves of the ON state (rectangle) and the OFF state (triangle) The retention results
The currents are recorded by applying a reading voltage of 1 V per sec.
The retention characteristics with an ON/OFF ratio of 103 at 300 K maintain until 2.5 × 104 sec at ambient conditions.
The experimental results can be extrapolated to 108 sec
The excellent date retention performance.
Summary 1; Nonvolatile memory devices based on semiconductor and core/shell nanoparticles embedded in a polymer layer
ZnO, CdSe/ZnS, and InP/ZnS nanoparticles embedded in the C60 or polymer layer
were formed by using a spin-coating technique.
The I-V curves for the OBD with Al/C60/ZnO nanoparticles embedded in a PI
layer/C60/ITO structure exhibited an electrical bistability with a maximum ON/OFF
ratio of 104 and good retention time.
The I-V curves for the OBD with Al/ZnO nanoparticles embedded in a PMMA
layer/ITO structure exhibited an electrical bistability with a maximum ON/OFF ratio
of 5 x 104, good switching performance, and excellent retention time.
I-V curves for the OBD containing CdSe/ZnS nanoparticles embedded in the C60
layer exhibited bistability properties.
Summary 2; Nonvolatile memory devices based on nanoparticles attached CNTs embedded in a polymer layer
ZnO and CdSe/ZnSe nanoparticles attached CNTs embedded in polymer layer were formed by using a spin-coating technique.
ZnO and CdSe/ZnSe nanoparticles were randomly attached on the surfaces of the MWCNTs.
OBDs containing ZnO and CdSe/ZnSe nanoparticles attached MWCNTs exhibited bistability properties with the maximum ON/OFF ratio of 4 x 104 and 104, respectively.
The conjugation of nanoparticles on the surfaces of the MWCNTs provides a channel that enhances the electron transfer efficiency to appear the current bistabiltiy.
OBDs with the Al/C60 molecular embedded in PMMA layer/ITO structure exhibited a current bistability with the maximum ON/OFF ratio of 3 x 103, good switching performance, and excellent memory retention.
End of the Semester
Cross-sectional bright-field TEM image for Ni1-xFex nanoparticles embedded in a polyimide layer
Ni1-xFex Nanoparticles
End of the Semester
Metal-insulator-semiconductor (MIS) behavior with charge trap regions
MIS memories
Flat-band voltage shift of the C-V curve 2 V
Electron accumulation and depletion
Capture electrons inside the nanoparticle
-2 0 2 4 6 8 10 120.0
2.0
4.0
6.0 Al / PI / nc-Fe0.8Ni0.2 / PI / n-Si (100)
CA
PAC
ITA
NC
E (p
F)
APPLIED VOLTAGE (V)
Capacitance-voltage curve
End of the Semester
e-Nano crystals
PolyimideMetal Gate
P-Si (100) Substrate
Source Drain
VGB
VDS
Transmit
Channel
Electron
e- e- e- e-
e- e- e- e- e- e- e- e-
+
+
-
-
A schematic diagram of the nano-floating gate flash memory utilizing nanocrystals formed in polyimide
Homework #9
고체전자공학 제 7 판
Chapter 9. 연습문제
문제 1, 문제 3
End of Semester
