Template for SFR Presentations

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Sensors Metrology

• SFR Workshop
• November 8, 2000
• E. S. Aydil, B. Dunn, K. Poolla,
• R. Smith and C. Spanos
• Berkeley, CA

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Sensor Milestones 2001

• September 30th, 2001
• Build and demonstrate Langmuir probe based
  on-wafer ion flux probe array using external
  electronics. (Aydil)
• Design and build a single MEMS based retarding
  field ion energy analyzer with external
  electronics. (Poolla)
• Design and fabricate first generation prototype
  MEMS sensor array. Bench test using Joule
  heating. (Smith)
• Demonstrate cut-and-paste approach for membrane
  arrays, LED arrays, and battery encapsulation.
  (Cheung)
• Develop thermally robust inorganic electrolyte.
  Lid added to battery encapsulation scheme. (Dunn)
  
• Build Microplasma generating system. Test with
  bulk optical components. (Poolla, Graves)

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Sensor Milestones 2002

• September 30th, 2002
• Build and demonstrate 8 on-wafer ion flux probe
  array in industrial plasma etcher with external
  electronics. (Aydil)
• Demonstrate MEMS based ion energy analyzer in
  plasma with external electronics. (Poolla)
• Integrate the inorganic electrolyte into the
  battery structure. Develop an in-situ lithium
  formation process. (Dunn)
• Build micro-optics for spectral analysis.
  Complete the preliminary designs for integrated
  MOES. (Poolla)

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Sensor Milestones 2003

• September 30th, 2003
• Integration of Si-based IC with sensor arrays.
  Characterize and test integrated MEMS ion sensor
  array. (Aydil, Poolla)
• Battery operation between room temperature and
  150C. Battery survivability to sensor soldering
  operation. (Dunn)
• Design and test integrated MOES. Calibration
  studies, sensor characterization. (Poolla,
  Graves)

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On-Wafer Ion Flux Sensors

• SFR Workshop
• November 8, 2000
• Berkeley, CA
• Tae Won Kim, Saurabh Ullal,
• Baosuo Zhou, and Eray Aydil
• University of California Santa Barbara
• Chemical Engineering Department

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Motivation and Goals

• Variation of ion bombardment flux and its spatial
  distribution with plasma conditions is critical
  to plasma etching.
• Ion flux uniformity at the wafer determines the
  uniformity of etching and etching profile
  evolution.
• There have been almost no measurements of the ion
  flux or ion flux distribution across the wafer as
  a function of both r and q in realistic etching
  chemistry.
• Design, build and demonstrate an on-wafer ion
  flux analyzer with external electronics capable
  of mapping J (r,q) on a wafer.

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On-Wafer Ion Flux Sensors Milestones

• September 30th, 2001
• Build and demonstrate Langmuir probe based
  on-wafer ion flux probe array using external
  electronics.
• September 30th, 2002
• Build and demonstrate 8 on-wafer ion flux probe
  array in industrial plasma etcher with external
  electronics.
• September 30th, 2003
• Integration of Si-based IC with sensor arrays.
  Characterize and test integrated MEMS ion sensor
  array. ( with Poolla)

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On-Wafer Ion Flux Probe Array

• 10 probes on 3 wafer
• Evaporated metal on PECVD SiO2 on Si wafer. Lines
  insulated by PECVD SiO2
• External electronics based on National
  Instruments SCXI platform
• The array is scanned at a rate of 1000
  Samples/sec (100 Samples/probe/sec)
• Lab View Interface

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Ion Flux Uniformity Measurements in an ICP Reactor
50 W
100 W
200 W

• Ion Flux as a function of r and q over the whole
  wafer is determined using Kriging extrapolation
  between the probes.
• Ion flux uniformity was measured in an
  inductively coupled plasma reactor in Ar
  discharge to demonstrate the probe operation. Qar
  8 sccm, P 50 mTorr, Probe bias -70V.

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Plasma Instability J (r,q,t)
t 1.5 s
t 0 s
t 3.2 s
t 4.5 s
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On-Wafer Ion Flux Measurements in a Cl2 Discharge
in Lam TCP 9400 Reactor

• Goal extend the measurements to a commercial
  reactor and realistic chemistry.

Measurement Probe (Biased _at_ -75V with respect to
reference)
Heavily Doped Si wafer (Reference)

• Ion Flux in Cl2 plasma increases as a function of
  exposure time to Cl2 plasma until it finally
  saturates.
• Changes in chamber wall conditions is likely to
  be responsible for the drift.
• SF6 plasma clean resets the chamber back to
  reproducible condition.

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Wall Probe
Plasma
Internal Reflection Crystal
Chamber Wall
From FTIR Spectrometer
To HgCdTe Detector

• IR radiation from a spectrometer is directed onto
  one of the beveled edges of an internal
  reflection crystal (IRC). The IR beam undergoes
  multiple total internal reflections from the
  crystals surface and emerges from the opposite
  beveled edge. In this way, IR spectra of films
  and species that are adsorbed on to the walls and
  the IRC are recorded.

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Monitoring the Walls During Cl2/O2 Etching of Si

• SiO2 film is deposited on reactor walls from the
  reaction of SiClx with O even in the absence of
  O2 in the feed gas quartz window or walls can be
  the source of Si and O.
• Sensor is sensitive to even a few Å of oxide on
  the walls.
• Sufficiently long SF6/O2 plasma removes the oxide
  film from the walls.

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Wall Cleaning/Conditioning Step Influences the
Ion Fluxes in the Subsequent Etching Steps
SF6 cleaning step
SF6O2 cleaning step

• Ion flux and its variation with time depends on
  the wall conditioning step
• If plasma reactor walls are cleaned/conditioned
  with SF6O2 Ion Flux remains steady for a
  longer time compared to conditioning with SF6
  only.

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Relation Between the Ion Flux, Gas Phase
Composition and Wall Deposits
Ion Flux
Cl SiClx
SiO2 on the Walls

• Ion Flux monitored using ion flux probe
• SiClx and Cl concentrations monitored using
  optical emission
• Wall deposition monitored using the MTIR-FTIR
  probe
• Oxygen plasma oxidizes the surface of the wafer
  and probe
• Cl2 plasma (no bias power) etches the oxide layer
  slowly compared to the Si.
• Drift in Ion Flux is due to changing wall
  conditions and plasma composition.

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Summary

• Designed and build an on-wafer ion flux probe
  array with external electronics.
• Demonstrated the use of the array for
• mapping ion flux uniformity in an Ar plasma.
• measuring spatiotemporal variation of the ion
  flux in presence of a plasma instability.
• Completed preliminary experiments in a commercial
  reactor.

2002 and 2003 Goals
Build and demonstrate 8 on-wafer ion flux probe
array in industrial plasma etcher with external
electronics by 9/30/2002. Integration of Si-based
IC with sensor arrays. Characterize and test
integrated MEMS ion sensor array. 9/30/2003.
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Lithium Batteries for Powering Sensor Arrays

• SFR Workshop
• November 8, 2000
• Bruce Dunn
• UCLA
• Student contributors
• Nelson Chong, Jimmy Lim, Jeff Sakamoto

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Outline

• Background
• Status at the end of August, 2000
• Present Directions/Future Goals

(C4H5N)n (xlt0.25)
Energy density (Wh/kg)
Cathode material selection
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Operational and Dimensional Requirements
In order to provide on-board power of SMART
wafers, a low profile, thermally stable, high
energy density battery must be used.
Temperature capability 150C. Vacuum (10-2
torr). Operating voltage gt 2.5 V Discharge
current 2mA. Discharge time gt 10 minutes. Low
Profile 500?m or less. Area Less than 3 cm x 3
cm. Rechargeable 10 cycles.
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Status as of August, 2000
Microprocessor
Year 2 Milestone Lithium battery encapsulated
in in wafer well
LED
Thermistor
Battery
Voltage regulator
Thickness profile
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Status as of August, 2000
Key Features
Batteries exhibit good energy density and
cycling behavior Operation at elevated
temperature and under vacuum Epoxy
encapsulation system enables low profile
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Status as of August, 2000
Year 2 Milestone Evaluation of battery
robustness
Excellent cycling characteristics at room
temperature
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Status as of August, 2000
90
Alternating discharge at 85 C/vacuum and room
temperature/atmosphere.
80
70
Discharge
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Temperature (oC)
Charge
50
40
2 mA discharge current to 2.5 volts.
30
20
0
5
10
15
20
25
30
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Time (hrs)
T 85 ?C 10-2 torr
Poor cycling behavior after operation at
85C/10-2 torr
Cycle
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SFR Program for 2000 - 2001

• Increase operating temperature to 150oC
• Replace polymer electrolyte with
  inorganic electrolyte
• a) Sol-gel method
• b) Composite inorganic/organic electrolyte

Both approaches based on confining liquid
electrolyte in fine pore network SiO2 network
provides rigidity Liquid electrolyte gives Li
conductivity
Li liquid electrolyte
SiO2 network
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SFR Program for 2000 - 2001
First results with organic/inorganic system are
very promising
Battery fabricated with new electrolyte very
good discharge characteristics achieved
Fumed Silica R805 particles/aggregates
Electrolyte 1M Li Imide 0.5 cc PC 2.5 cc PEGdm 250
Current work Increasing SiO2 content to improve
temperature resistance
Li conductivity gt 10-3 S/cm Thixotropic
properties
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SFR Program for 2000 - 2001
Improve encapsulation by incorporating a
silicon lid
Lid attached
Encapsulation with low viscosity epoxy
Viscosity400 to 500 cps at room
temperature. Cure time18 to 24 hrs at room
temperature
Encapsulation with 5 minute epoxy Cure time 5
mins.
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Summary and Future Work

• Accomplished Milestones for August, 2000
• Continued Improvements in Integrated Power
  Source
• a) Higher temperature operation/exposure
• Inorganic electrolyte (Sept. 2001)
• Integrate electrolyte into battery (Sept.
  2002)
• b) Improve battery fabrication/packaging
• Wafer lid (Sept. 2001)
• In-situ lithium formation (Sept. 2002)

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Microstructures for Temperature Uniformity
Mapping during PECVD
SFR Workshop November 8, 2000 Ribi Leung, Dwight
Howard, Scott D. Collins and Rosemary L.
Smith MicroInstruments and Systems Laboratory
(MISL) UC Davis
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Abstract

• The ever decreasing IC device geometry and
  increasing substrate diameters requires high
  degree of film thickness uniformity. PECVD rate
  is a function of Plasma Chemistry and Substrate
  (surface) Temperature. Uniformity depends on
  spatial control of process parameters, including
  plasma composition (gas flow rates and pressure),
  plasma energy (power), and substrate surface
  Temperature. Temperature uniformity is critical,
  since deposition rate typically follows an
  Arhenius dependence. The goal of this project is
  to design, fabricate and test T mapping stuctures
  for mapping surface Temperature during PECVD as
  an aid in process and tool development.

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Milestones(1 year project)

• September 30th, 2001
• To design and fabricate MEMS sensor array to
  record surface temperature variations.
• Demonstrate in PECVD tool.

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Thin Film Temperature (T) sensor
Metal thin film bilayer resistors
Au/Cr Interdiffusion

• Au/Cr, Al/Au, Al/Cr
• function records accumulated time
• at temperature as increase in R
• mechanism interdiffusion and/or formation of
  compound

Q1.13eV
A. Munitz, Y. Komem, The increase in the
electrical resistance of heat treated Au/Cr
films, Thin solid films, 71, 177-188 (1980).
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Metal Bilayer Resistor Pattern
500
µm
R0 670 ?
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Temperature Dependence of R
R/R0
RIE
PECVD
Al/Au/Cr
Au/Cr
Al/Cr
Temperature (C)
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Wafer T Mapping Demonstration

PolySilicon Etch Technics Parallel Plate RIE

• No Substrate Cooling
• fRF 160 kHz
• SF6 , 15 sccm, 150 mTorr
• RF power 200W

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Temperature vs Etch Uniformity
Temperature Map
Photograph of Wafer
hot
cool
Etch Incomplete, t 25 mins
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Temperature vs Etch Uniformity
Temperature Map
Photograph of Wafer
hot
cool
Etch Complete, t 31 mins
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Al/Cr for PECVD 2nd Phase Formation at T 290
R/R0
10
8
6
Al/Cr
4
Al/Au/Cr
2
1
Temperature, C
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Temperature Map PECVD Si3N4, 1200 Å
Al/Cr
Technics PECVD, Platen T 330 C, 10 min, SiH4
NH3
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MEMS Thermal Actuator (A)
d
8 R
Shield
R
d
Secondary Tip Motion
Arc 8 d

• Mechanical displacement with T
• Deflection recorded by masking of deposition by
  shield.
• Requires T structure gt T substrate.
• Calibration by Joule heating of legs with
  injected current.

I
I
800µm
Primary Tip Motion
I
I
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Polysilicon Microhinge
R
MUMPS Chip Photo
d
8R
d
2 Layer PolySi Process
poly1 poly2 anchor
Key
1 mm
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MEMS Thermal Actuator (B)
Al/polySi Bimetal Actuator
PECVD
?T
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This years tasks

• Fabricate and Test PolySi/Al Bilayer Resistors
• Measure R vs Temperature for PolySi/Al
• Measure PolySi/Al Composite Film Stress vs. T
• Design and Fabricate Thermal Actuator
• Demonstrate MEMS thermal actuator in PECVD

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Spatially Resolved Heat Flux Sensor Array on a
Silicon Wafer for Plasma Etch Processes
SFR Workshop November 8, 2000 Mason Freed, Costas
Spanos, Kameshwar Poolla Berkeley, CA
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Motivation

• Plasma etch processes are highly sensitive to
  wafer temperature, in terms of etch rate,
  selectivity, and anisotropy
• Heat delivered to the wafer has two principle
  sources ion flux bombardment, and exothermic
  chemical etch reactions
• Very difficult to measure these two quantities,
  spatially resolved, without wafer-mounted sensors
• 2001 GOAL Design, build, test array of heat flux
  sensors on a silicon wafer, with external
  electronics.

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Methods for Constructing Heat Flux Sensors

• Simple, layered heat flux gauge
• Problem for semiconductor dimensions and
  materials, ?T is very small

Incident heat flux (q? )
Dielectric, thermal conductivity ?
Temperature Sensors
t
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Possible Solution Thermopile

• Use series connection of many thermocouples to
  amplify temperature difference, giving a
  measurable output voltage.

- from Holmberg, Diller 1995
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Possible Solution Thermopile

• Benefits
• Sensitivity increases linearly with number of
  thermocouples
• Can use 100s or 1000s of them ? 1000X
  amplification
• Problems
• Sensor size is proportional to number of
  thermocouples
• Typical thermocouple materials are not part of
  standard CMOS process ? cant easily combine with
  electronics
• CMOS thermocouples fabricated from n-poly /
  p-poly are an order of magnitude less sensitive
• Assumes no conduction along thermocouple leads
  may not be a good assumption

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Possible Solution Gardon gauge

• Rotate the heat flow to travel laterally
  instead of vertically ? increase the effective
  dielectric thickness

Membrane Top View
?T
? depends on diameter squared!
D
Heat flow within thin dielectric membrane
Membrane Side View
Incident heat flux (q? )
Heat flow within membrane
Heat sink
Heat sink
w
?T
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Discrimination of Ion Flux / Etch Exothermicity

• Use two heat flux sensors, one with an exposed
  layer of etched material (exposed in diagram)
  and the other without this material (covered)
• Place sensors into Wheatstone bridge arrangement
• ?
• ? etched material must be low conductivity to
  avoid shorting the thermal path across the
  membrane

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Proposed heat flux sensor geometry

• Add antenna to funnel heat through the center,
  maximizing the temperature difference ?T

b
? now , a factor
10X higher
? now the conductivity of the top etched material
doesnt affect the operation of the sensor
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2002 and 2003 Milestones
Demonstrate heat flux sensor in plasma etch
environment, with external electronics, by
9/30/2002. Design wireless heat flux sensor wafer
and demonstrate it in plasma etch environment, by
9/30/2003.
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Microplasma Optical Emission Spectrometer (MOES)
on a chip
SFR Workshop November 8, 2000 Michiel Krüger,
David Hsu, Scott Eitapence, K. Poolla, C.
Spanos, D. Graves, O. Solgaard Berkeley, CA
2001 GOAL to build a microplasma generating
system and test it with bulk optical components
by 9/30/2001.
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Motivation and background

• Motivation
• Precise detection of compounds near substrate
  required during semiconductor manufacturing
• Organic compounds, emitted during DUV, can coat
  optics of stepper
• Background
• Small atmospheric pressure glow discharges can be
  used for species excitation.
• Glow discharge optical emission spectroscopy has
  long history in analytical chemistry

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Microplasma Optical Emission Spectrometer

• Basic idea
• OES from plasma reveals info about gas
  composition in chamber
• Interdisciplinary
• plasma physics and chemistry
• MEMS processing
• optics and metrology
• Inter-departmental
• chemistry
• electrical engineering
• mechanical engineering

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MOES (cont.)

• Generation of plasma with hollow cathode
• Generation of plasma possible if
  0.05ltp.Dlt10Torr.cm
• Smaller diameter (?75 mm) allows plasma
  generation at atmospheric pressure!
• This results in smaller sensor
• Many applications in (and outside!) IC processing
  industry (for example in lithography)

D
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Schematic of initial MOES experimental
configuration

• Combination of
• Bulk optical optical
• components
• Microplasma chamber,
• fabricated in Si substrate
• Light emitted from
• discharge is captured by
• lens and collimated onto grating
• Diffracted light from grating is
• focused on detector array to record spectrum

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First experiments plasma in 200mm hole, 100Torr
N2 ambient
molybdenum
chip
mica dielectric
vacuum chamber
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Currently fabricated in UCB Microlab

• Relatively simple to make
• XeF2 etch to achieve required depth and undercut
• Very small diameters, i.e. high pressure, possible

plasma
cathode
anode
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Fabrication process and challenges

• Fabrication
• OES cavity defined by deep reactive ion
  etching/XeF2 isotropic etch
• anode/cathode defined on front and backside of
  wafer (metal or doped Silicon)
• Challenges
• Microplasma stability and contamination
• Device sensitivity
• Packaging of device
• Exploration of pulsed operation to make
  autonomous power supply possible
• Integration of micro discharges onto chips for
  other applications

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2002 and 2003 Milestones

• Build micro-optics for spectral analysis.
  Complete the preliminary designs for integrated
  MOES, by 9/30/2002.
• Design and test integrated MOES. Calibration
  studies, sensor characterization, by 9/30/2003.