Integrated Inductors with Magnetic Materials for On-Chip Power … · – Single films increase...
Transcript of Integrated Inductors with Magnetic Materials for On-Chip Power … · – Single films increase...
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Integrated Inductors with Magnetic Materials for On-Chip Power Conversion
Donald S. GardnerCollaborators: Gerhard Schrom, Fabrice Paillet,
Tanay Karnik, Shekhar Borkar
Circuits Research Lab & Future Technology Research
Intel LabsIntel Corporation
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Outline• DC Voltage Converters
– Comparison of buck converters– Comparison of inductors with magnetic films
• Magnetic material properties– Magnetic hysteresis loops – Complex permeability spectra
• Inductors– Structure cross sections– Inductance measurements– Eddy current and skin effect– Sheet and shunt inductance
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Multi -Core Power Management
• Today - Coarse Grain Power Management– same voltage to all the cores, variable voltage
• Future – Fine Grain Power Management– each core or cluster of cores operates at the
optimum voltage
Voltage RegulatorVoltage Regulator
Voltage RegulatorVoltage Regulator
Voltage Regulator
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Two-Phase Buck Converter with Coupled Inductors
Inductor Power Losses
hyspp
ACLavgDCLOSS PI
RIRP +∆
×+×= −
12
22
AC loss componentDC loss component
Frequency dependentLoad dependent
frequencyf
dutycycleD
Lf
VDI
s
effs
outpp
==
−=∆
)1(_
Fundamentals of Power Elect ronics by Robert W. Erickson
Al or Cu wireswc insulator
magnetic material (CZT=CoZrTa)
tc
tm
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100~480 MHz Switching Regulator
DiscreteI nductors
Φ0
Φ1
Φ2
Φ3
VIN=1.2V, VOUT=0.9V, L=6.8nH, F=233MHz
4.3nsΦ0
Φ1
Φ2
Φ3
VIN=1.2V, VOUT=0.9V, L=6.8nH, F=233MHz
4.3ns
• High frequency• Hysteretic multi -phase topology 1ns response• 88% efficiency
Schrom, Gardner, et.al., IEEE PESC 2004 and IEEE VLSI Symp. 2004.
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Comparison of DC Converters
100x higher f
1000x SmallerL and C
[3] [4] [5] [6] [7] Pavo-1
Year 1996 1999 2000 2002 2002 2004
Tech [ µm] n/a 0.25 n/a 0.25 n/a 0.09
# phases 1 1 1 1 1 4
V IN [V] 4 3 4 2.5 3.6 1.2
V OUT [V] 3.3 2 3 1.4 2.7 0.9
f [MHz] 1.6 0.5 3 0.75 1.8 233
Eff. [%] 85 94 83.3 95 80 83.2
L TOT [µH] 3 10 1 15.2 1 0.0017
C [µF] n/a 47 1 21.6 n/a 0.0025
I MAX [A] 0.3 0.25 0.33 0.25 0.3 0.3
Area [mm 2] n/a 0.46 20 0.35 n/a 0.14
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Package -Integrated VR withIntel ® Core™2 Duo Processor
• Vin = 3V, Vout = 0~1.6V• f = 10~100 MHz• Current = 50 Amps / 75 Amps peak• Size = 37.6 mm2, 130 nm CMOS
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Efficiency Measurements
G. Schrom et. al., APEC, Paper #SP1.4.2, p. 75, 2010
• Package embedded air core inductors: 84.9%• Discrete powdered Fe core inductors:87.9%• Load adaptive bridge activation improved by >10%
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RF CMOS Integrated Circuit
Inductors make up 24% of this chipInductance density of spirals is small (<100 nH/mm2)
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Inductance Densities vs. Q -Factor from the Literature
Gardner, Jam ieson, et .al. I EEE Trans. Magnet ics, 45, pp. 4760, 2009.
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Magnetic Hystersis Loops for CoZrTa & NiFe
Slope µ = 1050
Slope µ = 3000
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Permeability vs. Applied Magnetic Field
Magnet ic anisot ropy H k has tw o com ponents: The int r insic induced anisot ropy from the deposit io n The dem agnet iz ing energy caused by the sam ple shape
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Complex Permeability Model
oiµωµρδ 2
=
High resistivity materials are needed to reduce the eddy currents and
increase the skin depth.
δδµµ
2
)1(tanh
)1(
2 dj
dji
++
=
δ = skin depthρ = resist iv ity of magnet ic filmω = frequencyµi = relat ive dc permeabilityd = film thickness
CoZrTa ρ = 1 0 0 µΩ- cm
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Real Com ponent I m aginary Com ponent
Permeability Spectra of CoZrTa
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Real Com ponent I m aginary Com ponent
Permeability Spectra of CoZrTa
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Inductance Modeling of Wire with Magnetic Material
Maximum Increase in Inductance
Magnetic Material
Magnetic Material
Wire
2 layers magnetic film ≤ µr ×1 layer magnetic film ≤ 2 ×
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Spiral and Transmission Line Inductors
Structures take advantage of the uniaxial magnetic anisotropy.
Hard
Easy
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Cross- Sectional Image of Inductor in 130 nm 6 -level Metal CMOS Process
CoZrTa
CoZrTa
Inductor Metal
Cu (M6)
Cu (M4)
Cu (M2)Cu (M1)
Cu (M3)
Cu (M5)
HardAxis Magnetic
Via
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Spiral Inductors with Single Magnetic Layer
Increase in inductance is small (10~30% at up to 9.8 GHz)
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Inductance increases by 9 ×
Spiral Inductors with Two Magnetic Layers
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Magnetic Flux Density At 1GHz
Unlam inatedCobalt a lloy
Lam inatedCobalt a lloy
Skin-depth effect lim its penet rat ion of B- field.Larger skin depth results in lower losses.
B- field (T)
4.0
3.63.22.82.42.01.61.20.80.40.0
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Inductance vs. Frequency of Spirals
Inductance density is 1,700 nH/mm 2
Roll off is from resonance (1/ √LC) of inductor.
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Spiral and Stripe InductorsUsing 5um thick Copper
Structures take advantage of the uniaxial magnetic anisotropy.
Hard
Easy
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Cross -Sectional Image of Inductorin 90 nm CMOS Process
9 0 nm 7 - level Meta l CMOS Process
Magnet icVia
Magnet icVia
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Cross- Sectional Image of Inductor
HardAxis
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Inductance increases by up to over 30 ×
Stripe Inductors With Thick Copper
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Inductance Modeling of Rectangular Line
≈
w
ltL m
r 20µµl = line lengthw = line widthtm = m agnet ic film thicknessµr = relat ive dc perm eability
1/l·Lsheet
1/Lshunt
1/L
Wtot
w
Eqn. from V. Korenivski and R. B. van Dover, JAP, v. 82 (10) , 1997
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Magnetic Via Widths
I nductance increases w ith via w idth, but the change becom es dim inishingly sm all.
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Sheet and Shunt Inductances
Sheet inductance is independent of the magnetic via width.Shunt inductance increases with increasing via width.
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Current Density At 100 MHz
Unlam inatedCobalt a lloy
Lam inatedCobalt a lloy
Eddy currents are reduced by lam inat ions.
J( A/ m 2 )
1E+ 9
9E+ 88E+ 87E+ 96E+ 85E+ 84E+ 93E+ 82E+ 81E+ 80E+ 0
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Analytical Modeling of Q -Factor
Thinner films give higher Q -factors, but lower inductance.
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Analytical Modeling of Q -Factor
Laminations increase the Q -factor.
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Quality Factor of Inductors With Laminated Magnetic Films
Peak quality factor is increased,But quality factor at lower frequencies decreased.
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Summary• DC Voltage Converters
– High -frequency buck converters– High inductance density needed– Low DC resistance important
• Magnetic materials– Complex permeability (real and imaginary) – Low hysteretic losses– CMOS compatibility (thermal, process compatibility)
• Inductors with magnetic material– Single films increase inductance by ≤30% up to 9.8 GHz– Magnetic vias – Sheet inductance vs. shunt inductance– 2 magnetic films increase inductance
• Over 30× compared to air -core• 200 nH inductors possible (1,700 nH/mm 2)
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For More Information
• IEEE Trans. Magnetics, 45, pp. 4760, 2009.
• Journal of Applied Physics, 103, pp. 07E927, Apr. 1, 2008.
• IEEE Trans. Magnetics, 43, pp. 2615, 2007.
• IEEE PESC 2004 and IEEE VLSI Symp. 2004.
• APEC, Paper #SP1.4.2, p. 75, 2010.
• Intl. Electron Devices Meeting (IEDM), pp. 221-224, 2006.
• IEEE Intl. Interconnect Technology Conference, pp.101–103, 2001.
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