1. 3rd Annual SFR Workshop & Review, May 24, 2001
8:30 – 9:00 Research and Educational Objectives / Spanos
9:00 – 9:45 CMP / Doyle, Dornfeld, Talbot, Spanos
9:45 – 10:30 Plasma & Diffusion / Graves, Lieberman, Cheung, Haller
10:30 – 10:45 break
10:45 – 12:00 Poster Session / Education, CMP, Plasma, Diffusion
12:00 – 1:00 lunch
1:00 – 1:45 Lithography / Spanos, Neureuther, Bokor
1:45 – 2:30 Sensors & Controls /Aydil, Poolla, Smith, Dunn, Cheung, Spanos
2:30 – 2:45 Break
2:40 – 4:30 Poster Session / all subjects
3:30 – 4:30 Steering Committee Meeting in room 373 Soda
4:30 – 5:30 Feedback Session
3rd Annual SFR Workshop & Review, May 24, 2001

2. Lithium Batteries for Powering Sensor Arrays
Nelson Chong, Jimmy Lim, Jeff Sakamoto and Prof Bruce Dunn
UCLA
Since November 2000:
Developed Inorganic/Organic nanocomposite electrolyte
Well behaved conductivity to 125oC
Batteries with nanocomposite electrolyte operate at 125oC
Batteries with Silicon lids
Epoxy attachment demonstrated
Plasma assisted approach designed
5/24/2001

3. Higher Operating Temperature Electrolyte
Replaced polymer electrolyte with
Inorganic/Organic Nanocomposite
sRT = 7 x 10-4 S/cm
s125C = 6 x 10-3 S/cm
Unique microstructure
SiO2/PMMA network
provides rigidity,
thermal stability
Li+ electrolyte confined
in fine pores
Well behaved conductivity
characteristics to 125oC
5/24/2001

4. Batteries Fabricated with Nanocomposite Electrolyte
Operation at Room Temperature
0.05 mA discharge
30 min Operation at 125oC
Thermal Cycling
Batteries cycle nicely and exhibit very good capacity
Batteries operate well at 125oC
Thermal cycling between RT and 125oC doesn’t influence capacity
5/24/2001

5. Silicon Lids Incorporated in Battery Encapsulation
Epoxy attachment
(Spanos, Poolla)
Plasma assisted bonding
(Cheung)
5/24/2001

6. Silicon Lid Attached by Epoxy
2 mA discharge
5/24/2001

7. Progress vs. Milestones
Develop Thermally Robust Electrolyte • Nanocomposite approach gives 125oC • Batteries demonstrate operation/survivability at 125oC
Next: • Higher temperature nanocomposite • Batteries to operate at 2 mA discharge
Incorporate Silicon Lid into Battery Encapsulation • Temperature testing of battery with epoxy-attached lid • Plasma-assisted bonding
5/24/2001

8. Mason Freed, Costas Spanos, Kameshwar Poolla
Spatially Resolved Heat Flux Sensor on a Silicon Wafer for Plasma Etch Processes
Mason Freed, Costas Spanos, Kameshwar Poolla
Berkeley, CA
2001 GOAL: Design, build, and test an array of heat flux sensors on a silicon wafer, with external electronics.
5/24/2001

9. Motivation
Plasma etch processes etch rate, selectivity, and anisotropy
Highly sensitive to wafer temperature
Heat delivered to the wafer from
ion flux bombardment : physical
exothermic etch reactions : chemical
Very difficult to separately measure these heat components spatially resolved
Need to use wafer-mounted sensors
5/24/2001

10. Sensor Geometry: Modified Gardon Gauge
 sensitivity depends on diameter squared
Heat flow
heat flux
Membrane,
thickness w
Incident heat q b
Antenna
Membrane
Sink
Sink T
5/24/2001

11. Discrimination of Ionic / Chemical Heating
Use two heat flux sensors, one with an exposed layer of etched material and the other covered
Place sensors in Wheatstone bridge arrangement:
antenna structure keeps this added material from adversely affecting the sensitivity
Router,exposed
Router,covered
Rinner,covered2
Vchem
Vphys + – + –
Rinner,exposed
Rinner,covered
Router,covered2
5/24/2001

12. First Process – High Built-In Stress Gradient
Warped Antenna
Etch
Holes
Membrane
5/24/2001

13. Second Process
Moved to poly antenna structure, from previous aluminum/oxide/photoresist stack
Enlarged wires to allow better printability
Switched to wet Aluminum etchant, to avoid aluminum/poly selectivity problem with Cl-based plasma etch
Modified layout to place etch holes closer together, and more evenly spaced
Modified layout to allow better matching between the inner and outer temperature-sense resistors
5/24/2001

14. Problems Solved
Next: 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.
5/24/2001

15. Electrical Impedance Tomography based Metrology
Michiel Krüger, K. Poolla, C. Spanos
Berkeley, CA
2001 GOAL: to demonstrate the feasibility of off-line metrology based on electrical impedance tomography by 9/30/2001.
5/24/2001

16. Problem formulation and motivation
Obtain spatial and temporal information of wafer state during processing, ex:
Etch rate/uniformity across wafer
Plasma induced potential on wafer surface
Wafer surface temperature
Motivation:
Spatial and temporal wafer state information provide useful information about process uniformity.
This information can be used for:
Diagnostics (drifts, detection of process instabilities)
Design (electrode configuration in plasma tools)
Control (to reduce process variability)
5/24/2001

17. Our Approach Start with “sensor wafer” with a thin
conductive layer on a dielectric film
Conductivity of wafer surface
is function of wafer state
Electrical measurements made
from pads at wafer edge
Data used to infer spatially
resolved film conductivity
Conductivity profile used
to deduce wafer state
Original conductivity
distribution
Potential distribution
due to forced current
flow through object
5/24/2001

18. Advantages Simple to Make and Use
Sensor wafer requires minimal processing
Thick film technology could be used
Simple electronics
Can be integrated with on-board power and data storage/communications
General Technique with many applications
Etch rate/uniformity sensor, plasma induced potential at wafer surface, temperature at wafer surface
Problem reduces to inverse problem in electrical impedance imaging
5/24/2001

19. Electrical Impedance Tomography (EIT)
Basic idea:
Force fixed current through interior W of an object from electrodes at the edge W
Reconstruct conductivity profile from measurements of potential u on the boundary W of object
From Maxwell’s equation: •(su)=0
Widely used in
biomedical applications
geology
non-destructive product testing
Equipotential line
Electrode W W I
5/24/2001

20. Implementation: etch rate/uniformity
Conductivity of doped Poly-Si function of thickness
Etch rate (thickness) variations result in nonuniform conductivity
Simple process flow
Oxidize wafer
Deposit Poly-Si and pattern
Deposit Al and pattern
Easy to test in XeF2
etcher
Al electrode
Oxidized wafer
doped
Poly-Si
5/24/2001

21. Implementation: plasma potential
Design, fabricate and test etch rate sensor with temperature compensation, by 9/30/2002.
Design, fabricate and test plasma potential sensor, by 9/30/2003.
Al electrode
gate oxide
Al gate Si
source
drain
Vgs > Vt ,  = f(Vgs)
plasma
source
Vgs < Vt ,   0
drain
gate
5/24/2001

22. On-Wafer Ion Flux Sensors Tae Won Kim, Saurabh Ullal, and Eray Aydil University of California Santa Barbara Chemical Engineering Department
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.
5/24/2001

23. 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)
5/24/2001

24. Summary of Progress and Research Activities
Designed and build an on-wafer ion flux probe array with external electronics and data acquisition on 3” and 8” wafers.
Demonstrated the use of these arrays for
mapping ion flux uniformity in an Ar plasma.
measuring spatio-temporal variation of the ion flux in presence of a plasma instability.
Completed preliminary experiments in a commercial reactor with 8” wafers.
Tae Won Kim has been at Lam Research in Fremont since March 2001 to implement the probe array on 8” wafers to collect data Lam TCP 9400 Reactor and will stay there through the summer and may be the rest of 2001.
5/24/2001

25. 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
5/24/2001

26. Plasma Instability: J+ (r,q,t)
t = 0 s
t = 1.5 s
t = 3.2 s
t = 4.5 s
5/24/2001

27. 200 mm on-wafer ion flux sensors
Ion flux uniformity was measured in a LAM TCP 9400 reactor to demonstrate the probe operation. (50 sccm He, 300 W, 30 mTorr.
5/24/2001

28. Specific Goals
Modify data acquisition to be used with rf bias on the electrostatic chuck.
Use the probe array to study the factors that affect the plasma and etching uniformity in Cl2/O2 etching of Si.
Specifically, the goal will be to understand the role of
etching products
the wall conditions
feed gas composition
5/24/2001

29. Microstructures for PECVD Temperature Mapping Dwight Howard, Eunice Lee, Scott D. Collins and Rosemary L. Smith MicroInstruments and Systems Laboratory (MISL) UC Davis
Small Feature Reproducibility: film thickness uniformity is critical
Uniformity depends on spatial control of:
plasma composition (gas flow rates and pressure)
plasma energy (power)
substrate surface Temperature
-- Project Goals --
Design, fabricate and test thin film microstuctures for mapping surface temperature during PECVD, for process monitoring.
minimize tool hardware modifications
process compatibility
low cost manufacture, and data retrieval
5/24/2001

30. Milestones (1 year project)
September 30th, 2001
To test thin film resistor sensor array in PECVD.
To design and fabricate MEMS sensor array to record surface temperature variations.
Bench test MEMS array
5/24/2001

31. Thin Film Temperature (T) Sensor Metal, thin film, bilayer resistors
500Å Cr
SiO2
Silicon
Al/Cr or Al/PolySi Resistor
Effect: permanent change in R vs. T
Mechanism: interdiffusion, alloying, or annealing
5/24/2001

32. 2nd Phase Formation at T = 290 C
Al/Cr Resistors
2nd Phase Formation at T = 290 C
R/R0 10
1.3 8
1.25
1.2 6
1.15 4
1.1 2
1.05
1.0 1
130
150
170
190
210
230
250
270
290
310
330
350
Temperature (C)
5/24/2001

33. Temperature Mapping Demonstration Al/Cr Resistors, 120 nm PECVD Si3N4
5/24/2001

34. Al/PolySi R vs. T
5 min
10 min
20 min
5/24/2001

35. Al / PolySi Temp Map 100 nm PECVD Si3N4
Degrees, C
400
350
300
250
Platen T=300C
300 < T < 380 C
5/24/2001

36. MEMS Thermal Actuator (work in progress)
Aluminum, 1 mm
Cantilever Beam Example
Silicon, 2 mm
Silicon
Thermal expansion coefficient mismatch --> strain --> displacement
T= T0
T1 >T0
TC>T1
TC depends on geometry of cantilever.
Array of microstructures designed to have varying TC.
Readout can be optical imager.. in situ or post processing.
5/24/2001

37. Layer Transfer Technology for Micro-System Integration Changhan Yun, Yonah Cho, Adam Wengrow, and Nathan Cheung Berkeley, CA
Detector
Sensor array
Electronics
Interconnects
Battery
Resonators
Photon emitters
Low-Temperature assembly process enables integration of dissimilar microsystems (embedded photon emitter, energy source, sensors, electronics)
5/24/2001

38. LED Array Transfer with Laser Liftoff
1. Bond receptor onto GaN sapphire
2. Laser Liftoff (LLO)
3. Acetone bath
4. Bond to any substrate
Interfacial decomposition
Thermal
detachment (~40°C)
receptor
wafer
adhesive
adhesive
LED Si
Al2O3
Laser beam
Transfer of LED layers from sapphire to silicon or plastic substrate
5/24/2001

39. Blue LED Transferred on Silicon Substrate
From a distance
Under a microscope
probe tip
probe tip
No luminosity degradation after layer transfer!
5/24/2001

40. Summary of Progress and Research Activities
Low-temperature Si layer transfer using mechanical cleavage (see poster for details)
Wafer-scale transfer of quantum-well GaN LED arrays onto Si substrate with no degradation of luminosity and device performance
2002 and 2003 Goals
Incorporate light emitting devices on sensor wafers
Demonstrate layer transfer for subsystem encapsulation (e.g. batteries)
Design interconnection schemes between the dissimilar microsystems
Demonstrate integration of signal and data processing systems with photonics and MEMS
5/24/2001

41. Comprehensive Simulation Tool for CMP processes Carlo Novara, Kameshwar Poolla, Costas Spanos
Build MATLAB based CMP model
Pad pressure
Spin speeds
Slurry comp
Pad state
Initial topography
CMP
Process
Removal rate
Slurry state
Pad state
Topography
Parameter tuning
& adaptation
RTR
Metrology
Tools
5/24/2001

42. Motivation & Approach Model uses The Challenge Approach
OEM : internal diagnostics, design, sensitivity assessment
Production: maintenance scheduling, recipe optimization
The Challenge
Complexity: large numbers of unmeasurable parameters in model need to be estimated from data and tuned periodically
Limited availability of metrology to tune model
Approach
Evaluate sub-system sensitivity with simulation studies to drive model reduction => fewer parameters
Confirm sensitivities experimentally
5/24/2001

43. Research Plan Focus on Copper process 8/01 – basic model in place
1/02 – sensitivity studies complete
8/02 – data driven model validation
5/24/2001

44. Model-based Diagnosis
Real-time equipment model
Diagnostic Engine
Real time monitoring of key
equipment variables
processing
equipment
5/24/2001

45. Hardware Setup in the Berkeley Microlab
Workstation
SECII
Lam 9400
OES
sensor
Z-scan
sensor
5/24/2001

46. Wafer State Modeling of Uniformity & Etch Rate: combined sensor signals give the best results
source
Wafer
state
Significant signals
R2 adj.
OES
signals
Uniformity
997 nm, 559 nm, 1049 nm, 974 nm
.9470
Etch Rate
355nm, 207 nm, 202 nm, 210 nm
.9765
SECS-II Signals
TCP load cap, HBr stpt, cham press
.8325
TCP load cap, Cl2, RF line imp #1
.8941
ZSCAN
RF signals
V1, I1
.4491 I5
.217
All
355 nm, 207 nm, I4, load coil pos
.9845
5/24/2001

47. Future Directions in Diagnosis
Deploy automated fault detection system using high sampling rate RF fingerprinting.
Study automated generation of syntactic analysis rules for RF fingerprinting.
Study systems of real-time instability detection and plasma stabilization control;
Perform field studies of automated OES classification for fault diagnosis.
5/24/2001

48. Lithography Process Monitoring through CD Profile Metrology
Inputs
Inputs Range
Silicon Substrate
Si Oxide
Polysilicon
ARC
Resist
Mask
Exposure Dose
10-15 (mJ/cm²)
Focus Position
(um)
Partial Coherence
04-0.7
PEB Time
54-66 (sec)
PEB Temperature
(°C)
Side Wall Angle (SWD)
10%CD
50%CD
90%CD
Outputs:
10%CD
50%CD
90%CD
SideWallAngle
5/24/2001

49. Simulated Data from PROLITH
Use PROLITH to replace experimental data
Advantage: convenient for generating large number of data of different recipes required by model development
Disadvantage: not exactly the same as a real process, must be tuned by experimental data in practice.
200
400
600
800
1000
1200
1400
1600
1800
2000
100
150
250
300
350
# of data point
50% CD (nm)
exposure dose increase
5/24/2001

50. Some Diagnostic Results (Time Series Estimation)
1st order autoregressive model
All other parameters are fixed and known
Exposure use the same model as above. Focus is fixed but unknown, other input parameters are fixed and known
5/24/2001

51. 3rd Annual SFR Workshop & Review, May 24, 2001
8:30 – 9:00 Research and Educational Objectives / Spanos
9:00 – 9:45 CMP / Doyle, Dornfeld, Talbot, Spanos
9:45 – 10:30 Plasma & Diffusion / Graves, Lieberman, Cheung, Haller
10:30 – 10:45 break
10:45 – 12:00 Poster Session / Education, CMP, Plasma, Diffusion
12:00 – 1:00 lunch
1:00 – 1:45 Lithography / Spanos, Neureuther, Bokor
1:45 – 2:30 Sensors & Controls /Aydil, Poolla, Smith, Dunn, Cheung, Spanos
2:30 – 2:45 Break
2:40 – 4:30 Poster Session / all subjects
3:30 – 4:30 Steering Committee Meeting in room 373 Soda
4:30 – 5:30 Feedback Session
3rd Annual SFR Workshop & Review, May 24, 2001