how a single defect can affect silicon nano-devices …...how a single defect can affect silicon...
TRANSCRIPT
![Page 2: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/2.jpg)
The Big Idea
• As MOS-FETs continue to shrink, single atomic scale defects are beginning to affect device performance
Source Drain
Gate
![Page 3: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/3.jpg)
Outline
• The impact of a single atom on a MOSFET
• Locating a single atom in a transistor
• The potential for a single atom
![Page 4: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/4.jpg)
Review of MOS-FETs I
Heavily n-doped Source and Drain S emi-
conductor
O xide
M etal
Lightly p-doped channel
Source Drain
Gate
e-
e- e-
e- e-
e- e-
e- e-
e- e-
e- e- e-
e- e-
e- e- e-
e-
e-
e-
e- e- e- e- e-
e- e-
e- e- e-
e- e-
e- e- e-
e-
e-
e- e- e-
e- e-
e- e- e-
e-
e-
h+
h+
h+ h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+
h+ h+ h+
h+
![Page 5: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/5.jpg)
Review of MOS-FETs II Typical MOS-FET Curve - 300 K
0
1
2
3
-1.5 -1 -0.5 0 0.5 1
VGate (V)
I (n
A)
D
Gate
S
Negative
Holes Accumulate h+ h+ h+ h+
h+ h+ h+ h+ h+ h+
h+ h+ h+ h+ h+ e- e-
e- e-
e- e-
e- e- e-
e-
e- e- e-
e- e- e
-
e- e- e-
e-
e-
e-
e- e-
e-
S D
Gate
Positive
Electrons Invert e- e-
e- e-
e- e-
e- e-
e- e- e-
e-
e-
e-
e- e-
e- e- e-
e-
e- e- e-
e- e- e- e- e-
e- e- e- e- e-
e- e- e- e-
e-
Threshold Voltage (VT)
![Page 6: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/6.jpg)
Not just shrinking….
High-κ dielectrics
Planar to 3D Strain
e- e- e- e-
e- e- e-
Source
Gate
Source Drain
Gate
3 nm Silicon Dioxide
Hafnium Oxide
Source Drain
Gate
![Page 7: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/7.jpg)
Atomic Scale Defects
Source Drain
Dopant
Gate
e-
e- e-
e- e-
e- e-
e- e-
e- e-
e- e- e-
e- e-
e- e- e-
e-
e-
e-
e- e- e- e- e-
e- e-
e- e- e-
e- e-
e- e- e-
e-
e-
e- e- e-
e- e-
e- e- e-
e-
e- e- e- e- e-
e- e- e- e-
e-
Leakage to gate
Random Dopants change VT
3 nm
Trap
e-
![Page 8: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/8.jpg)
Threshold Voltage
M Pierre, et al. “Single-donor ionization energies in a nanoscale CMOS channel,” Nature Nano, 2010
VG
I
0 1 -1
ΔVT
10 nm
~ 10s of dopants
25 devices studied, ΔVT ≈ 1 V
![Page 9: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/9.jpg)
Ordered Dopant Arrays
Heavily n-doped Source and Drain
Source Drain
Dopant
Shinada, et al. Nature (2005)
VT
N
Random
Std. Dev. = 0.3 V
VT
N
Ordered
Std. Dev. = 0.1 V
![Page 10: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/10.jpg)
Outline
• The impact of a single atom on a MOSFET
• Locating a single atom in a transistor
• The potential for a single atom
![Page 11: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/11.jpg)
Looking for a single atom
Annular dark-field scanning-TEM
Need to chop up device to look at it
K. Van Benthem, et al. “Three-dimensional imaging of individual hafnium atoms inside a semiconductor” Applied Physics Letters, 87 03104 (2005)
![Page 12: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/12.jpg)
The Basic Idea: Cryogenic Temperatures
E
z EC
EF e- e-
Source Drain
e-
Dip: Quantum Dot
Peaks: Tunnel Junction
e- e-
12 Dopant
![Page 13: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/13.jpg)
The Basic Idea: Coulomb Blockade
E
EC
EF eVSD ≈ 1 meV e-
VG
I G
GC
eV
13
aFV
C
V
eC
G
G 1001.0
10 19
Drain Source
Gate
![Page 14: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/14.jpg)
Lower Gates • Heavily doped Poly • 10 – 40 nm long • 3 independent gates
Nanowire • ~20 nm x 20 nm x 500 nm • Surrounded by 20 nm SiO2
Upper Gate • Heavily doped Poly
A. Fujiwara, et al. APL 88, 053121 (2006)
14
![Page 15: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/15.jpg)
Positive voltage on upper gate inverts wire
Poly Upper Gate
Poly Lower Gate
Silicon Dioxide
Crystalline Silicon
e-
e- e-
e- e-
e- e- e-
e- e- e- e-
e- e- e- e-
e- e- e- e-
e- e- e- e-
e- e-
e- e- e-
e- e- e- e- e- e-
e- e- e- e-
e- e- e- e-
e-
LGS LGC LGD
Upper Gate
Source Drain
T = 4.4 K VSD = 2 mV VLGS,C,D = 0
![Page 16: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/16.jpg)
Negative voltages on lower gates form tunnel barriers
Poly Upper Gate
Poly Lower Gate
Silicon Dioxide
Crystalline Silicon
e-
e- e-
e- e-
e- e- e-
e- e- e- e-
e- e-
e- e- e-
e- e- e-
e- e-
e- e- e- e-
e- e-
e- e-
e- e- e-
e- e-
e- e-
e-
LGS LGC LGD
Upper Gate
Source Drain
-0.8 -0.7 -0.6 -0.5 -0.4
10-2
100
10-1
10-3
VLGD
(V)
g (
S)
LGD
Peaks correspond to transport through QDs
e- e- e- e- e- e- e- e- e- e- e- e-
T = 40 mK VUG = 1 V VLGC,D = 0
![Page 17: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/17.jpg)
Device 1: T =39 mK VSD = 1 mV VLGS,C = 0
Measure current while scanning VUG and VLGD
17
0.8
20
.86
0.9
0.9
4
10
-3
10
-2
VU
G (V
)
I (nA)
Periodic Coulomb blockade oscillations
![Page 18: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/18.jpg)
A Device 1: T =39 mK VSD = 1 mV VLGS,C = 0
• 2 flavors of QDs
– A: few periods, more strongly coupled to LGD
– B: many periods, more strongly coupled to UG
18
B
![Page 19: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/19.jpg)
Measure Gate Capacitances
LGD (aF) UG (aF) Ratio LGD/UG LGC (aF)
Dev. 1: Dot A 2.3 + 0.3 - 1.3 1.3 + 0.2 - 0.6 1.71 ± 0.02 < 0.1
Dev. 1: Dot B 3.2 ± 0.2 7.9 ± 0.3 0.41 ± 0.01 < 0.1
19
![Page 20: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/20.jpg)
Locate the Dot
Simulated ½ device in FASTCAP
LGC LGD
UG
Si Wire
20
![Page 21: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/21.jpg)
Locate the Dot
LGC LGD
UG
Si Wire
21
LGD (aF) UG (aF) Ratio LGD/UG LGC (aF)
Dev. 1: Dot B 3.2 ± 0.2 7.9 ± 0.3 0.41 ± 0.01 < 0.1
• Measure gate capacitances
• Simulate capacitances to
1 nm slices of wire
• Integrate between z1 and z2
• For what z1 and z2 does 𝐶𝑠𝑖𝑚 = 𝐶𝑚𝑒𝑎𝑠
for all gates
𝐶𝑠𝑖𝑚 = 𝑑𝐶
𝑑𝑧
𝑧2
𝑧1
𝑑𝑧
![Page 22: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/22.jpg)
Location of Dots
Between LGD and UG
LGC LGD
UG
Si Wire B
0
-20 -50
A
A B
z1 = -40 ± 3 z2 = -19 ± 3
22
0
20 95
z1 = 17 ± 1
z2 = 87 ± 2
50 Location in nm
LGD
![Page 23: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/23.jpg)
Dopant Location?
Deduced conduction band modulation
LGC LGD
UG
Si Wire A B
EF
EC
23
Dopants?
We see same QDs in multiple devices -The cause appears systematic -Strain from temperature change and oxide growth -Could help make faster finFETs
![Page 24: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/24.jpg)
Finding a Dopant
• Very similar technique has been used to located individual dopants and interface traps
– Nathaniel Bishop, et al; “Triangulating tunneling resonances in a point contact” Arxiv 1107.5104 (2011)
![Page 25: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/25.jpg)
Outline
• The impact of a single atom on a MOSFET
• Locating a single atom in a transistor
• The potential for a single atom
![Page 26: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/26.jpg)
Ultimate Transistor?
Source Drain
Gate
Similar to:
Cheng Cen, et al. “Oxide Nanoelectronics on Demand” Science 323, 1026 (2009)
Martin Fueschsle, et al. “Spectroscopy of few-electron single-crystal silicon quantum dots” Nature Nano, 5, 502 (2010)
Dopant
![Page 27: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/27.jpg)
Beyond the transistor
• World looks different on the atomic-scale
– Quantum regime
• This is a problem for current transistors
– Tunneling to the gate
• Could this “quantumness” become useful
![Page 28: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/28.jpg)
Quantum Search
Number of Boxes
10
1000
Old Computer
10 μs
1000 μs
New Computer
10 ns
1000 ns
Quantum Computer
10 ns
100 ns
“Classical” Computer: To search x100 boxes takes x100 as long
“Quantum” Computer: To search x100 boxes takes x10 as long
![Page 29: How a single defect can affect silicon nano-devices …...How a single defect can affect silicon nano-devices Ted Thorbeck tedt@nist.gov The Big Idea •As MOS-FETs continue to shrink,](https://reader030.vdocument.in/reader030/viewer/2022011818/5e8b3c5e70a6104a2a752d95/html5/thumbnails/29.jpg)
Conclusions
• MOSFETs are reaching the point where the placement of a single atom can affect device performance
• New tools allow the location of a single atom to be determined within a MOSFET
• The quantum nature of a single atom could one day allow for much more powerful devices