Radiant Technologies, Inc.Autonomous Memory Advanced Concepts for [617881]

Radiant Technologies, Inc.Autonomous Memory Advanced Concepts for
Evaluating Material and Device
Characteristics
using Cantilevers
Rev B
Radiant Technologies, Inc.
February 8, 2016
17th US-Japan Seminar on Dielectrics and Piezoelectrics

Radiant Technologies, Inc.Autonomous Memory Summary
GOAL :
Create a test fixture and a sample geometry for that
fixture to measure piezoelectric coefficients of thin films
accurately and reliably .

REQUIREMENTS :
-Inexpensive – Photonic sensor or LVDT
-Reproducible – No variance for re-loading same sample .
-Simple to operate
-Versatile – thin film or bulk, production or research
-Shippable – calibrated on first test after shipping .

Radiant Technologies, Inc.Autonomous Memory e31 from Cantilevers
. •George Stoney in 1909 created an equation describing the bending of a
beam from the contraction of a thin film on one surface of the beam.

•Use a piezoelectric film in the Stoney Equation to predict how far the
beam will bend with voltage.

•Move the beam with a voltage while measuring tip displacement allows
the derivation of e31 where e31 equals d31 / s11.

•Both Kanno [Sensors and Actuators A 107 (2003) 68 –74 ] and Mazzalai [International
Symposium on Applications of Ferroelectrics – ISAF , Prague, Czech Republic; 07/2013] converted
the Stoney Equation for thin piezoelectric films. 0V Vsat

Radiant Technologies, Inc.Autonomous Memory Y = Young’s modulus of the silicon (substrate) in Gigapascals
( silicon = 169GPa)

 = Poisson’s ratio for the silicon (substrate) [silicon = 0.064]

tSi = Thickness of the silicon substrate in centimeters (usually 550µm for Radiant
wafers)

tp = Thickness of the piezoelectric film in centimeters (not shown)

V = V olts applied to piezoelectric capacitor

cf = Ratio of capacitor width to cantilever width (0.6 for Radiant cantilevers)

x1 = Distance from clamp point to the end of the piezoelectric capacitor in meters.

x2 = Distance from clamp point to the displacement sensor.
Mazza lai Equation

Radiant Technologies, Inc.Autonomous Memory e31 Fixture
The cantilever geometry must fit a specific pattern . Radiant will provide
GDSII layout files to anyone who would like to try this.
Drive
Return
Earth Ground
Free Silicon Substrate
Clamped No Capacitance

Radiant Technologies, Inc.Autonomous Memory Cantilever Design
•Parasitic capacitance is reduced by a hole in the bottom electrode .
6.35mm
Foot BE Contact 19.05mm TE Contact
Clamp 25.4mm
Sensor Point 41.96mm 72mm
BE
FE
TE
FE
Etch

Radiant Technologies, Inc.Autonomous Memory ±1% Test to Test
-1.0-0.500.51.01.52.02.53.03.54.04.5
-50 -40 -30 -20 -10 0 10 20 30 40 50Twenty Sequential Loops of 2.0um PNZT & 1.5um 52/48Microns
Volts
•20 tests each for 2µm 4/20/80 PNZT and 1.5µm 52/48 PZT
•Sequential tests without unloading the sample between tests. 1.5µm 52/48 PZT
-14.2 C/m2 2.0µm 4/20/80 PNZT
-9.74 C/m2

Radiant Technologies, Inc.Autonomous Memory
-1.0-0.500.51.01.52.02.53.03.54.04.55.0
-50 -40 -30 -20 -10 0 10 20 30 40 5010 Tests Each of 2um 4/20/80 PNZT vs 1.5um 52/48 PZT
[ Unloaded then Re-loaded Between Each Test ]Microns
Volts±2.5% Between Loads
•10 tests each for 2µm 4/20/80 PNZT and 1.5µm 52/48 PZT
•Each sample unloaded and reloaded between tests 1.5µm 52/48 PZT
-14.2 C/m2 2.0µm 4/20/80 PNZT
-9.74 C/m2

Radiant Technologies, Inc.Autonomous Memory Pmax & Dmax for 10 Loads
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
0 5 10 15 20 25 Microns
Loop Number PNZT Dmax vs Loop#
Unload then Re -load
PNZT -Dmax
PNZT Dmax -reload
(re-load) = 1.2%
0 10 20 30 40 50
0 5 10 15 20 25 uC/cm2
Loop Number PNZT Pmax vs Loop#
Unload then Re -load
PNZT -Pmax
PNZT Pmax -reload
(re-load) = 0.05% 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
0 5 10 15 20 25 Microns
Loop Number 52/48 Dmax vs Loop#
Unload then Re -load
52/48 -Dmax
(re-load) = 0.87%
0 5 10 15 20 25 30 35 40 45 50
0 5 10 15 20 25 uC/cm2
Loop Number 52/48 Pmax vs Loop#
Unload then Re -load
52-48Pmax
53/48 Pmax -reload
(re-load) = 0.17% BLUE dots are tip
displacements for
20 sequential
tests.

RED dots are
polarizations for
20 sequential
tests.

GREEN circles
are the same
measures taken
with unload and
re-load between
each test.

Radiant Technologies, Inc.Autonomous Memory
00.51.01.52.02.53.03.54.04.5
0 5 10 15 20 25 30 35 40 45 500.5um vs 1.0um vs 2.0um @ 250kV/cmMicrons
Volts2.0um 4/20/80 PNZT: Sensor Value 1.0um 4/20/80 PNZT: Sensor Value
0.5um 4/20/80 PNZT: Sensor ValueDisplacement vs Thickness
•All three samples made from the same gel.
•All three fabricated on identical substrates . 2.0µm
-8.7 C/m2 1.0µm
-11.0 C/m2
0.5µm
-11.4 C/m2

Radiant Technologies, Inc.Autonomous Memory e31 vs Thickness
•E31 goes down as the voltage increases because of the paraelectric
effect on polarization .

Radiant Technologies, Inc.Autonomous Memory PNZT Microstructure
•The measured e31 values are consistent for the polycrystalline PZT
used to fabricate these cantilevers .

Radiant Technologies, Inc.Autonomous Memory Measuring Bulk Materials
•A bulk ceramic cantilever can be shaped to match the e31
geometry .
•The bulk cantilever must be glued to a substrate so it
becomes a monomorph .

Radiant Technologies, Inc.Autonomous Memory
-2024681012141618
-20 -15 -10 -5 0 5 10 15 20Compare Philtec to MTI
[ 1um-thick 4/20/80 PNZT e31 Cantilever ]Microns
VoltsMTI: Single-Trace Math Filter: 1 Philtec: Single-Trace Math Filter: 1Compare Sensors
•Different sensors can be used to increase sensitivity or lower cost.
•The plot above shows two photonic sensors from different companies
measuring the same cantilever .

Radiant Technologies, Inc.Autonomous Memory Physics
•Virgin polarization and displacement loops for 1.0µm
PNZT .

-30-20-100102030
012345
-40 -30 -20 -10 0 10 20 30 40First Pass on Virgin 2um 4/20/80 PNZTµC/cm2 MicronsProc. Hyst Proc. Disp

Radiant Technologies, Inc.Autonomous Memory Future Objectives
•Independent verifi cation of the the e31 values by other
organizations .

•Evaluate less expensive displacement sensors .

•Acquire new top electrode mask with smaller actuator area
to test very thin films of 2500 Å or less.

•Develop a more complex version of the Stoney Equation to
include the effects of electrode stiffness, additional layers,
and other electrode geometries .