Design Limits for Thin Dielectric Film Capacitors

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Design Limits for Thin Dielectric Film
Capacitors Rensselaer Team  

Prof. Eugene J. Rymaszewski , Prime
Investigator Prof. Toh-Ming Lu, Co-Investigator
(processing) Pushkar Jain (leveraged from
CPES) Jasbir Juneja Vinay Bhagwat Dr.
Matthew Nielsen (now GE CRD) Dr. Jin Young Kim
(now TI)
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Objectives

• Novel high performance decoupled power
  distribution planes (high C, very low L) and
  embedded discrete capacitors.
• Achieve
• capacitance densities in several hundred nF/cm2
  range,
• effective inductances in pH range,
• breakdown voltages above 10-25 V, and
• leakage current densities below 1 ?A/cm2.
• Contain within acceptable limits the
  electromagnetic interactions between the power
  distribution planes and the signal connections
  which traverse through these planes.

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Accomplishments
Empirically determined interdependency between er
and EBR. Derived breakdown voltage vs.
capacitance density (µF/cm2) for er of 3 to 3000
and films between 10 nm and 100 µm
thick. Measured effects of the film thickness on
I-V characteristics. Measured the role of Oxygen
concentration during sputtering. Designed and
used GHz characterization test vehicles.
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micro-roughness of the metal plate surfaces
Related consideration
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Empirical equation EBR20/ er0.5 From E
V/d where, E Electric field (MV/cm)
V Voltage (V) d Thickness
(cm) and Ce0 er A/d where, C Capacitance
(F) e0 8.85x10 -14 ( F/cm) A
Area of capacitor (cm2) Vmax 60 d0.5
1/(C/A)0.5, and Vmax 1.7 ?r0.5 1/(C/A)
These relationships delineate the design space
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Design space
Vmax 60 d0.5 1/(C/A)0.5
Vmax 1.7 ?r0.5 1/(C/A)
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Experimental data
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No thickness dependency of the dielectric constant
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Causes of the lower breakdown voltage/field E
BR lower than 20/er 0.5 Materials
micro-structure amorphous, crystalline,
columnar Materials defects, e.g. metal in
insulator (e.g. _at_ low Oxygen) Non-conformal
deposition and micro-roughness of the bottom
metal surface caused by an enhancement of the
metal to polymer bond  
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The local breakdown with thin films
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Experimental data
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Columnarity occurance on films thicker than
approx. 1 1.5 µm
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I-V Characteristics of Tantalum oxide films
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Effect of oxygen concentration during sputtering
on er
Temperature dependency of er of Ta2O5 thin films
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Reduction of the power-distribution
inductance Several placements of a decoupling
capacitor in a close proximity (external) to
the IC chip embedded in the semiconductor body
of the chip embedded within wiring planes of the
chip interposed between the chip and its
packaging High-K thin film between power and
ground planes
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High (medium) K dielectric thin film is
sandwiched between power and ground
planes Signal lines travels through the thin
film increased capacitance to power/ground
planes may be offset by higher apertures
diameter, but larger apertures decrease the
value of decoupling capacitor
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Characterization vehicle
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S21 with
different probe positions
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Frequency dependence of dielectric constant
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Current endeavors

• Effects, causes and control (if needed) of
  columnarity
• Interaction between the power distribution
  planes and
• the signal lines transiting through these planes
• Integration of these structures
• Lower manufacturing costs than those by
  sputtering