Template for SFR Presentations

Template for SFR Presentations

3rd Annual SFR Workshop, November 8, 2000 8:30 9:00 9:50 10:10 11:00 12:00 1:00 1:50 2:40 9:00 9:50 10:10 11:00 11:50 1:00 1:50 2:40 4:30 Research and Educational Objectives / Spanos Plasma, Diffusion / Graves, Lieberman, Cheung, Haller break Lithography / Spanos, Neureuther, Bokor Sensors & Metrology / Aydil, Poolla, Smith, Dunn

lunch CMP / Dornfeld, Talbot, Spanos Integration and Control / Poolla, Spanos Poster Session and Discussion, 411, 611, 651 Soda 3:30 4:30 Steering Committee Meeting in room 373 Soda 4:30 5:30 Feedback Session 2 Sensors & Metrology SFR Workshop November 8, 2000 E. S. Aydil, B. Dunn, K. Poolla, R. Smith and C. Spanos Berkeley, CA 11/8/2000 3 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) 11/8/2000 4 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) 11/8/2000

5 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) 11/8/2000 6 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 11/8/2000

7 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 in realistic etching chemistry. Design, build and demonstrate an on-wafer ion flux analyzer with external electronics capable of mapping J+ (r,) on a wafer. 11/8/2000 8 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) 11/8/2000 9 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 11/8/2000

10 Ion Flux Uniformity Measurements in an ICP Reactor 50 W 100 W 200 W 0.134 0.131 0.128 0.126 0.123 0.120 0.118 0.115 0.112 0.110 0.107 0.104 0.102 0.099 0.097 0.094 0.091

0.089 0.086 0.083 0.081 0.078 0.075 0.073 0.070 2 Ion Flux (mA/cm ) Ion Flux as a function of r and 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. 11/8/2000 11 Plasma Instability: J+ (r,,t) t=0s t = 1.5 s t = 3.2 s

t = 4.5 s 11/8/2000 12 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 @ 75V with respect to reference) 5.0 10m To rr/10 0Cl 2 /5Ar /800T CP/0BP 2 I sat (mA /cm ) 4.5 4.0 3.5

3.0 Heavily Doped Si wafer (Reference) 0 5 00 10 00 15 00 20 00 25 00 Tim e (sec) 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.

11/8/2000 13 Wall Probe Plasma Internal Reflection Crystal Chamber Wall E = E0 exp {-z/dp} n1 E n2 A Cl z Cl

O Si d To HgCdTe Detector From FTIR Spectrometer 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. 11/8/2000 14 Monitoring the Walls During Cl2/O2 Etching of Si Si-O 0.8 Absorbance

0.6 After Cl2/O 2 etching of Si Si-Cl After SF6/O 2 plasma 0.4 O2Si-Cl 0.2 Si-F 0.0 600 800 1000 1200 1400 -1

Wavenumbers (cm ) SiO2 film is deposited on reactor walls from the reaction of SiCl x 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 of oxide on the walls. Sufficiently long SF6/O2 plasma removes the oxide film from the walls. 11/8/2000 15 Wall Cleaning/Conditioning Step Influences the Ion Fluxes in the Subsequent Etching Steps SF6 cleaning step SF6+O2 cleaning step 4.5 4.5 10mTo rr/10 0Cl 2 /5Ar/800T CP/0BP

10mTo rr/10 0Cl 2 /5Ar/800T CP/0BP 2 I sat (mA /cm ) 4.0 2 I sat (mA /cm ) 4.0 3.5 3.5 3.0 3.0 0 60

1 20 Time (sec) 1 80 0 60 1 20 1 80 Time (sec) Ion flux and its variation with time depends on the wall conditioning step If plasma reactor walls are cleaned/conditioned with SF 6+O2 : Ion Flux remains steady for a longer time compared to conditioning with SF 6 only. 11/8/2000

16 Relation Between the Ion Flux, Gas Phase Composition and Wall Deposits Ion Flux Cl & SiClx 10000 10m To rr/10 0Cl 2 /5Ar/800T CP/0BP Raw Emission Intensity 2 I sat (mA /cm ) 4.0 3.5 3.0 60 1 20 Time (sec)

SiCl SiCl Cl 5000 0 0 12 SF6 SF6+O2 Integr ated Si-O absorbance 4.5

SiO2 on the Walls 1 80 0 20 40 60 80 Time (sec) 100 120 140 160 10

8 6 4 2 0 0 50 1 00 1 50 2 00 Time (sec) 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. 11/8/2000 17

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. 11/8/2000 18 Lithium Batteries for Powering Sensor Arrays SFR Workshop November 8, 2000 Bruce Dunn UCLA Student contributors:

Nelson Chong, Jimmy Lim, Jeff Sakamoto 11/8/2000 19 Outline Background Status at the end of August, 2000 Present Directions/Future Goals V6O13 (0

600 400 200 0 1 11/8/2000 2 3 4 5 6 7 Cathode material selection 8 9 20 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: > 2.5 V Discharge current: 2mA. Discharge time: > 10 minutes. Low Profile: 500m or less. Area: Less than 3 cm x 3 cm. Rechargeable; 10 cycles. 11/8/2000 21 Status as of August, 2000 Microprocessor LED Thermistor Year 2 Milestone: Lithium battery encapsulated in

in wafer well Voltage regulator Battery Thickness profile 11/8/2000 22 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 11/8/2000 23

Status as of August, 2000 Year 2 Milestone Evaluation of battery robustness 1 mA charge E (Volts) 4.0 discharge capacity (mAh) 4.5 Discharge Capacity 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5

0 0 3.5 2 4 6 8 cycle number 3.0 2.5 2 mA discharge 2.0 0 5000 10000

Time (Sec) 11/8/2000 15000 Excellent cycling characteristics at room temperature 10 12 24 Status as of August, 2000 90 Alternating discharge at 85 C/vacuum and room temperature/atmosphere. Discharge 70 60

Charge 50 40 2 mA discharge current to 2.5 volts. 30 20 0 5 T = 85 C 10-2 torr 10 15 20 Time (hrs) 25

Poor cycling behavior after operation at 85C/10-2 torr 30 35 capacity (mAh) Temperature (oC) 80 5 4 3 2 Minimum acceptable capacity 1 0 11/8/2000

85 oC/vacuum 25 oC/atmosphere 0 1 2 Cycle 3 4 5 25 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 Li+ liquid electrolyte

SiO2 network 11/8/2000 Both approaches based on confining liquid electrolyte in fine pore network SiO2 network provides rigidity Liquid electrolyte gives Li+ conductivity 26 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 Li+ conductivity > 10-3 S/cm Thixotropic properties 11/8/2000

Current work: Increasing SiO2 content to improve temperature resistance 27 SFR Program for 2000 - 2001 Improve encapsulation by incorporating a silicon lid Encapsulation with 5 minute epoxy Cure time= 5 mins. 11/8/2000 Lid attached Encapsulation with low viscosity epoxy Viscosity=400 to 500 cps at room temperature. Cure time=18 to 24 hrs at room temperature 28 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) 11/8/2000 29 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 11/8/2000 30 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. 11/8/2000 31 Milestones (1 year project) September 30th, 2001 To design and fabricate MEMS sensor array to record surface temperature variations. Demonstrate in PECVD tool. 11/8/2000 32

Thin Film Temperature (T) sensor Metal thin film bilayer resistors Au/Cr Interdiffusion 500 Au 500 Cr SiO2 Silicon Q=1.13eV * Au/Cr, Al/Au, Al/Cr function: records accumulated time at temperature as increase in R mechanism: interdiffusion and/or f ormation of compound R / t e Q / kT *A. Munitz, Y. Komem, The increase in the electrical resistance of heat treated Au/Cr films, Thin solid films, 71, 177-188 (1980). 11/8/2000 33 Metal Bilayer Resistor Pattern

500 m R0 = 670 11/8/2000 34 Temperature Dependence of R R/R0 RIE 1.3 PECVD Al/Au/Cr 1.25 Au/Cr 1.2

Al/Cr 1.15 1.1 1.05 1.01 50 70 90 110 130 150 170 190 210 230 250 300 Temperature (C) 11/8/2000 35 Wafer T Mapping Demonstration PolySilicon Etch Technics Parallel Plate RIE No Substrate Cooling fRF =160 kHz

SF6 , 15 sccm, 150 mTorr RF power = 200W 11/8/2000 36 Temperature vs Etch Uniformity Photograph of Wafer Temperature Map hot cool Etch Incomplete, t = 25 mins 11/8/2000 37 Temperature vs Etch Uniformity Temperature Map Photograph of Wafer hot

cool Etch Complete, t= 31 mins 11/8/2000 38 Al/Cr for PECVD 2nd Phase Formation at T 290 R/R0 10 8 6 Al/Cr 4 Al/Au/Cr 2 1 50 100

150 200 250 300 Temperature, C 11/8/2000 350 400 39 Temperature Map PECVD Si3N4, 1200 Al/Cr Technics PECVD, Platen T= 330 C, 10 min, SiH4 + NH3 11/8/2000 40

MEMS Thermal Actuator (A) 8R Shield d R d Secondary Tip Motion Arc ~ 8 d Mechanical displacement with T I Deflection recorded by masking of deposition by shield. 800m I Requires T structure > T substrate.

Primary Tip Motion I I 11/8/2000 Calibration by Joule heating of legs with injected current. 41 Polysilicon Microhinge R MUMPS Chip Photo d 8R d 2 Layer PolySi Process Key 1 mm

11/8/2000 poly1 poly2 anchor 42 MEMS Thermal Actuator (B) Al/polySi Bimetal Actuator PECVD T 11/8/2000 43 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

11/8/2000 44 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 11/8/2000 45 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. 11/8/2000 46 Methods for Constructing Heat Flux Sensors Simple, layered heat flux gauge: Incident heat flux (q ) t Dielectric, thermal conductivity Temperature Sensors T t q Problem: for semiconductor dimensions and materials, T is very small: 2m 0.001K W

T 1000 m2 1.38 W mK 11/8/2000 47 Possible Solution: Thermopile Use series connection of many thermocouples to amplify temperature difference, giving a measurable output voltage. - from Holmberg, Diller 1995 11/8/2000 48

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 11/8/2000 49 Possible Solution: Gardon gauge Rotate the heat flow to travel laterally instead of vertically increase the effective dielectric thickness T q D2 16w Membrane Top View

T depends on diameter squared! D Heat flow within thin dielectric membrane Membrane Side View Incident heat flux (q ) Heat sink w Heat flow within membrane T 11/8/2000 Heat sink 50

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: Router,exposed Router,covered Vchemical Vionflux + Rinner,exposed + Rinner,covered2

Rinner,covered Router,covered2 Vchemical qexothermic , Vionflux qionflux etched material must be low conductivity to avoid shorting the thermal path across the membrane 11/8/2000 51 Proposed heat flux sensor geometry Add antenna to funnel heat through the center, maximizing the temperature difference T b Incident heat flux (q ) Heat flow within membrane Heat sink Heat sink T 2

D T q ln D , a factor 2ln D now 10X higher 8kw b b

now the conductivity of the top etched material doesnt affect the operation of the sensor 11/8/2000 52 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. 11/8/2000 53 Microplasma Optical Emission Spectrometer (MOES) on a chip

SFR Workshop November 8, 2000 Michiel Krger, 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. 11/8/2000 54 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 11/8/2000

55 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 11/8/2000 56 MOES (cont.) Generation of plasma with hollow cathode plasma cathode dielectric

D mm anode Generation of plasma possible if: 0.05

detector Light emitted from lens array discharge is captured by lens and collimated onto grating Diffracted light from grating is focused on detector array to record spectrum 11/8/2000 grating 58 First experiments: plasma in 200m hole, 100Torr N2 ambient Molybdenum anode molybdenum Mica dielectric (drilled hole) chip mica dielectric

vacuum chamber 11/8/2000 Silicon chip with 200m hole and aluminum cathode 59 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 50-200m 0.7m 1m 200m poly-Si SiO2 substrate cathode anode 11/8/2000

plasma 60 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 11/8/2000

61 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. 11/8/2000

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