IEEE Solid-State Circuits Magazine - Spring 2016 - 52
to their unique characteristics.
STT-MRAM has advantages of fast
write/read speed (<10 ns) and
long endurance (>1015 cycles) that
PCRAM/RRAM lacks; thus, STTMRAM is attractive to replace SRAM
or embedded DRAM in the last-level
cache. Today's STT-MRAM has >30 F2
cell area; thus it is not economically
competitive to replace DRAM for
main memory. In the long run, with
the reduction of write current of
the STT-MRAM, it may have the
the cycling endurance for the main
memory system can be reduced to
1010 cycles; PCRAM/RRAM may meet
this requirement with the help of a
strong error-correct code. It is not
economically promising for PCRAM/
RRAM to directly replace the NAND
flash for standalone SSD due to a
higher cost per bit. State-of-the-art
two-dimensional (2D) NAND flash
has been scaled down to around 15
nm in 2015, while the 3D stackable
NAND flash is emerging [54], [55].
Ultimately, the 3D stacked PCRAM/RRAM may
have potential to serve as high-end enterprise
SSD if cost per bit is not of highest priority
but performance is.
potential to achieve 6 F2 cell area.
Then it may become attractive to
replace DRAM for main memory
because it does not need the periodic refresh. On the other hand,
PCRAM/RRAM has advantages of
a smaller cell area (4 F2~6 F2) and,
thus, a larger capacity than STTMRAM; however, its endurance is
typically in the range of 10 6-10 10
cycles; thus it is more suitable for
the storage-class memory filling the
gap between the main memory and
the storage memory (e.g., SSD). With
the smart architectural wear-leveling
techniques [53], the requirement of
Twenty-four-, 32-, and 48-layer (up
to 256 Gb) 3D NAND flash chips featuring MLC have been demonstrated
[56]-[58]. On the market, 3D NAND
flash-based SSD has been commercialized. Although at the single
device level, PCRAM/RRAM outperforms NAND flash in many aspects
such as faster programming speed,
smaller programming voltage, and
better endurance. The key challenge
for PCRAM/RRAM to compete with
NAND flash is the integration density or, more importantly, the cost
per bit. To approach similar device
density as the 3D NAND flash, a
technology path toward the 3D
stackable PCRAM/RRAM is required.
Ultimately, the 3D stacked PCRAM/
RRAM may have potential to serve
as high-end enterprise SSD if cost
per bit is not of the highest priority
but performance is.
3D Integration of PCRAM/RRAM
There are two monolithic 3D integration approaches for PCRAM and/or
RRAM technologies: one is based on
stacking the conventional horizontal
cross-point array layer by layer [59], as
shown in Figure 6(a), which is referred
to as 3D X-point as in the Intel/Micron
announcement [51]; the other is the
vertical pillar structure with RRAM
sandwiched between the pillar electrodes and multilayer plane electrodes [60], as shown in Figure 6(b).
This vertical 3D RRAM concept is
similar to today's vertical channel 3D
NAND flash. Figure 6(c) shows the
cross-section microscopic schematic
of the vertical RRAM prototype cell
[61] by cutting through one pillar electrode: the RRAM cells are formed at
the sidewall of the pillar electrode and
in contact with the plane electrodes
(highlighted by the red-dash circle),
and there is one cell at each metal
layer. The fabrication cost of the first
approach using the stacked horizontal
cross-point array is relatively higher
because the number of lithography
steps increases with the number of
the layers; thus, the fabrication cost
remains high as the lithography step
and mask are expensive.
Word Line (Plane)
Word Line
Pillar Electrode
TiN
Memory
Cell
Memory
Cell
SiO2
HfOx
Pt
Select Line
VRRAM
SiO2
Pt
Bit Line
Bit Line
(a)
40 nm
(b)
SiO2
(c)
Figure 6: The schematics of (a) a stacked 3D horizontal cross-point array and (b) a 3D vertical cross-point array. (c) The microscopic cross section of a 3D vertical rram prototype by cutting through one pillar electrode. adapted from [61].
52
S P R I N G 2 0 16
IEEE SOLID-STATE CIRCUITS MAGAZINE
Table of Contents for the Digital Edition of IEEE Solid-State Circuits Magazine - Spring 2016
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover1
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover2
IEEE Solid-State Circuits Magazine - Spring 2016 - 1
IEEE Solid-State Circuits Magazine - Spring 2016 - 2
IEEE Solid-State Circuits Magazine - Spring 2016 - 3
IEEE Solid-State Circuits Magazine - Spring 2016 - 4
IEEE Solid-State Circuits Magazine - Spring 2016 - 5
IEEE Solid-State Circuits Magazine - Spring 2016 - 6
IEEE Solid-State Circuits Magazine - Spring 2016 - 7
IEEE Solid-State Circuits Magazine - Spring 2016 - 8
IEEE Solid-State Circuits Magazine - Spring 2016 - 9
IEEE Solid-State Circuits Magazine - Spring 2016 - 10
IEEE Solid-State Circuits Magazine - Spring 2016 - 11
IEEE Solid-State Circuits Magazine - Spring 2016 - 12
IEEE Solid-State Circuits Magazine - Spring 2016 - 13
IEEE Solid-State Circuits Magazine - Spring 2016 - 14
IEEE Solid-State Circuits Magazine - Spring 2016 - 15
IEEE Solid-State Circuits Magazine - Spring 2016 - 16
IEEE Solid-State Circuits Magazine - Spring 2016 - 17
IEEE Solid-State Circuits Magazine - Spring 2016 - 18
IEEE Solid-State Circuits Magazine - Spring 2016 - 19
IEEE Solid-State Circuits Magazine - Spring 2016 - 20
IEEE Solid-State Circuits Magazine - Spring 2016 - 21
IEEE Solid-State Circuits Magazine - Spring 2016 - 22
IEEE Solid-State Circuits Magazine - Spring 2016 - 23
IEEE Solid-State Circuits Magazine - Spring 2016 - 24
IEEE Solid-State Circuits Magazine - Spring 2016 - 25
IEEE Solid-State Circuits Magazine - Spring 2016 - 26
IEEE Solid-State Circuits Magazine - Spring 2016 - 27
IEEE Solid-State Circuits Magazine - Spring 2016 - 28
IEEE Solid-State Circuits Magazine - Spring 2016 - 29
IEEE Solid-State Circuits Magazine - Spring 2016 - 30
IEEE Solid-State Circuits Magazine - Spring 2016 - 31
IEEE Solid-State Circuits Magazine - Spring 2016 - 32
IEEE Solid-State Circuits Magazine - Spring 2016 - 33
IEEE Solid-State Circuits Magazine - Spring 2016 - 34
IEEE Solid-State Circuits Magazine - Spring 2016 - 35
IEEE Solid-State Circuits Magazine - Spring 2016 - 36
IEEE Solid-State Circuits Magazine - Spring 2016 - 37
IEEE Solid-State Circuits Magazine - Spring 2016 - 38
IEEE Solid-State Circuits Magazine - Spring 2016 - 39
IEEE Solid-State Circuits Magazine - Spring 2016 - 40
IEEE Solid-State Circuits Magazine - Spring 2016 - 41
IEEE Solid-State Circuits Magazine - Spring 2016 - 42
IEEE Solid-State Circuits Magazine - Spring 2016 - 43
IEEE Solid-State Circuits Magazine - Spring 2016 - 44
IEEE Solid-State Circuits Magazine - Spring 2016 - 45
IEEE Solid-State Circuits Magazine - Spring 2016 - 46
IEEE Solid-State Circuits Magazine - Spring 2016 - 47
IEEE Solid-State Circuits Magazine - Spring 2016 - 48
IEEE Solid-State Circuits Magazine - Spring 2016 - 49
IEEE Solid-State Circuits Magazine - Spring 2016 - 50
IEEE Solid-State Circuits Magazine - Spring 2016 - 51
IEEE Solid-State Circuits Magazine - Spring 2016 - 52
IEEE Solid-State Circuits Magazine - Spring 2016 - 53
IEEE Solid-State Circuits Magazine - Spring 2016 - 54
IEEE Solid-State Circuits Magazine - Spring 2016 - 55
IEEE Solid-State Circuits Magazine - Spring 2016 - 56
IEEE Solid-State Circuits Magazine - Spring 2016 - 57
IEEE Solid-State Circuits Magazine - Spring 2016 - 58
IEEE Solid-State Circuits Magazine - Spring 2016 - 59
IEEE Solid-State Circuits Magazine - Spring 2016 - 60
IEEE Solid-State Circuits Magazine - Spring 2016 - 61
IEEE Solid-State Circuits Magazine - Spring 2016 - 62
IEEE Solid-State Circuits Magazine - Spring 2016 - 63
IEEE Solid-State Circuits Magazine - Spring 2016 - 64
IEEE Solid-State Circuits Magazine - Spring 2016 - 65
IEEE Solid-State Circuits Magazine - Spring 2016 - 66
IEEE Solid-State Circuits Magazine - Spring 2016 - 67
IEEE Solid-State Circuits Magazine - Spring 2016 - 68
IEEE Solid-State Circuits Magazine - Spring 2016 - 69
IEEE Solid-State Circuits Magazine - Spring 2016 - 70
IEEE Solid-State Circuits Magazine - Spring 2016 - 71
IEEE Solid-State Circuits Magazine - Spring 2016 - 72
IEEE Solid-State Circuits Magazine - Spring 2016 - 73
IEEE Solid-State Circuits Magazine - Spring 2016 - 74
IEEE Solid-State Circuits Magazine - Spring 2016 - 75
IEEE Solid-State Circuits Magazine - Spring 2016 - 76
IEEE Solid-State Circuits Magazine - Spring 2016 - 77
IEEE Solid-State Circuits Magazine - Spring 2016 - 78
IEEE Solid-State Circuits Magazine - Spring 2016 - 79
IEEE Solid-State Circuits Magazine - Spring 2016 - 80
IEEE Solid-State Circuits Magazine - Spring 2016 - 81
IEEE Solid-State Circuits Magazine - Spring 2016 - 82
IEEE Solid-State Circuits Magazine - Spring 2016 - 83
IEEE Solid-State Circuits Magazine - Spring 2016 - 84
IEEE Solid-State Circuits Magazine - Spring 2016 - 85
IEEE Solid-State Circuits Magazine - Spring 2016 - 86
IEEE Solid-State Circuits Magazine - Spring 2016 - 87
IEEE Solid-State Circuits Magazine - Spring 2016 - 88
IEEE Solid-State Circuits Magazine - Spring 2016 - 89
IEEE Solid-State Circuits Magazine - Spring 2016 - 90
IEEE Solid-State Circuits Magazine - Spring 2016 - 91
IEEE Solid-State Circuits Magazine - Spring 2016 - 92
IEEE Solid-State Circuits Magazine - Spring 2016 - 93
IEEE Solid-State Circuits Magazine - Spring 2016 - 94
IEEE Solid-State Circuits Magazine - Spring 2016 - 95
IEEE Solid-State Circuits Magazine - Spring 2016 - 96
IEEE Solid-State Circuits Magazine - Spring 2016 - 97
IEEE Solid-State Circuits Magazine - Spring 2016 - 98
IEEE Solid-State Circuits Magazine - Spring 2016 - 99
IEEE Solid-State Circuits Magazine - Spring 2016 - 100
IEEE Solid-State Circuits Magazine - Spring 2016 - 101
IEEE Solid-State Circuits Magazine - Spring 2016 - 102
IEEE Solid-State Circuits Magazine - Spring 2016 - 103
IEEE Solid-State Circuits Magazine - Spring 2016 - 104
IEEE Solid-State Circuits Magazine - Spring 2016 - 105
IEEE Solid-State Circuits Magazine - Spring 2016 - 106
IEEE Solid-State Circuits Magazine - Spring 2016 - 107
IEEE Solid-State Circuits Magazine - Spring 2016 - 108
IEEE Solid-State Circuits Magazine - Spring 2016 - 109
IEEE Solid-State Circuits Magazine - Spring 2016 - 110
IEEE Solid-State Circuits Magazine - Spring 2016 - 111
IEEE Solid-State Circuits Magazine - Spring 2016 - 112
IEEE Solid-State Circuits Magazine - Spring 2016 - 113
IEEE Solid-State Circuits Magazine - Spring 2016 - 114
IEEE Solid-State Circuits Magazine - Spring 2016 - 115
IEEE Solid-State Circuits Magazine - Spring 2016 - 116
IEEE Solid-State Circuits Magazine - Spring 2016 - 117
IEEE Solid-State Circuits Magazine - Spring 2016 - 118
IEEE Solid-State Circuits Magazine - Spring 2016 - 119
IEEE Solid-State Circuits Magazine - Spring 2016 - 120
IEEE Solid-State Circuits Magazine - Spring 2016 - 121
IEEE Solid-State Circuits Magazine - Spring 2016 - 122
IEEE Solid-State Circuits Magazine - Spring 2016 - 123
IEEE Solid-State Circuits Magazine - Spring 2016 - 124
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover3
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover4
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019winter
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018fall
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018spring
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018winter
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2014
https://www.nxtbookmedia.com