Wireless Metrology in Semiconductor Manufacturing

Transcription

1 1 Wireless Metrology in Semiconductor Manufacturing Costas J. Spanos Seminar

2 2 Outline Historical perspective Hardware and software applications Breakthroughs that have yet to be realized Distributed control and diagnostics Hardware requirements

3 3 Past And Present Ideas and even patents circulated in the industry since the early 90s. No known implementation since UCB work started in late 1997 Commercialized in 2000 by OnWafer Technologies Founders from UCB and LAM Research BakeTemp for Post Exposure Bake PlasmaTemp An expanding software applications suite

4 4 Smart Sensor Wafers In-situ sensor array, with integrated power and telemetry Applications: process control, calibration, diagnostics & monitoring, process design

5 5 Sacrificial, On-wafer Sensors Temperature Compensated Design of Etch Rate Sacrificial Sensor Each sensor has a buried temperature reference I I Exposed Buried V temp V th

6 6 Wired Proof of Concept Implementation 100mm

7 7 Results - bakeplate Wafer placed on bakeplate, R s measured for both sensors

8 8 Results - XF 2 Etch Temperature-induced offset cancelled 13Å average

9 9 Wireless Prototype ~1999 Off-the Shelf Components, Ni on Al, Solder Paste Mount LED batteries PIC voltage regulator thermistor resistor capacitors 4 Sensors 4 o C Accuracy 2 o C Precision 1 oo C Resolution Primary Batteries No Memory Fixed Behavior ~15grams/ 100mm 5mm

10 10 Thermal Stress Tests on Calibrated Plate

11 11 Autonomous Passage Through Wafer Track Wafer arrives at at chill chill plate Non-uniform bake Non-uniform cooling Wafer leaves bake plate

12 12 RF isolation of wafer; isn t it ugly? Standard temperature wafer covered with layer of epoxy Epoxy is transparent to infrared: LED can be used for data transmission

13 13 Test results in plasma: RF 50W, 0.76 Torr, O 2 sensor 1 sensor 2 Word s first Wireless Plasma Monitoring Late 1999! sensor 3 sensor 4

14 14 Test results in plasma: RF 100W, 0.76 Torr, O 2 sensor 1 sensor 2 Word s first Wireless ~High Power Plasma Monitoring! sensor 3 sensor 4

15 15 A Commercial Smart Dummy? (Sept 2000) Courtesy of OnWafer Technologies, Inc.

16 16 Outline Historical perspective Hardware and software applications Breakthroughs that have yet to be realized Distributed control and diagnostics that go beyond lithography and etch Hardware requirements

17 17 Today: The BakeTemp Sensor Wafer polyimid SiO Sensors Sensors 4 o C Accuracy 0.05 o C Accuracy 2 o C Precsion 0.02 o C Precision 1 oo C Resolution oo C Resolution Primary Batteries Secondary module Batteries No Memory Memory Fixed Behavior Programmable/Adaptive Behavior ~15grams/ Courtesy 5mm OnWafer Technologies ~1.5grams/ 3mm

18 18 Much more than you ever wanted to know about Post Exposure Bake Overshoot Steady Heating Cooling 200mm ArF 90nm 130 o C 60sec Courtesy OnWafer Technologies Chill

19 19 Today: The PlasmaTemp Sensor Wafer Demonstrated in up to 7,000W Chambers Reusable Clean and safe enough to be adopted by all the top tier fabs

20 20 On-Wafer Plasma Monitoring 200mm Poly Etching Routine He Reduced He main etch pre-etch over etch de-chuck

21 21 Cool chuck - 200mm Poly Etching main etch Temperature fluctuations during main etch

22 22 Can see rotating magnetic field! phase delay in temp fluctuation Can calculate B-field period Can see rotation is clockwise

23 23 What are the Killer Apps? Temperature Monitoring has intuitive diagnostic value for some users. To expand use from Pilot to Production, we must address different, routine needs. Calibration Acceptance SPC/SQC

24 24 Post Exposure Bake Track Equipment Complexity is Increasing 10 Years of Product Evolution Single Zone Control Multi-Zone Control PEB Evolved from a Single Zone to Multi-Zone Control System Why?

25 25 PEB Hotplate Thermal Profile Optimization System Plate Type Specific Thermal Profile Modeling Engine AutoCal Baseline Thermal Profile Condition Input Input BakeTemp & OnView Offset Generator Engine Output OnWafer Technologies Offset Values Optimized for Both Within-Plate and Plate-to-Plate Thermal Profile Uniformities

26 26 PEB Temp Control Before After Target = 120 o C o C o C 16 plates, 120 ºC Target OnWafer Technologies

27 27 Spatial PEB/CD Distribution Correlation Plotting both the bake plate temperature trajectory and R 2 from temperature-cd correlation against bake time: Max R 2 during the transient heating period Continued high R 2 during steady state due to poor temperature control in single-zone plate design

28 28 PEB Hotplate Critical Dimension Optimization System Plate Type Specific Thermal Profile Modeling Engine AutoCal Resist & Litho Cell Specific CD Modeling Engine AutoCD Baseline Thermal Profile Condition Input Input BakeTemp & OnView Offset Generator Engine Input Input Output Baseline CD Profiles per Plate Offset Values Optimized for Both Within-Plate and Plate-to-Plate Critical Dimensions Uniformities Customer Provided OnWafer Technologies

29 29 CDU Improvement AutoCD AutoCal 1 POR Across Plate OnWafer Technologies Plate to Plate AutoCal AutoCD POR

30 30 What we learned about Lithography Weight / Form Factor module electronics, height, wafer flatness Precision Speed Equipment Compatibility Contamination COST OF OWNERSHIP Lifetime Ease of Use

31 31 Killer Lithography Applications 0 Monitor/Diagnose Multi-zone plates, complex exhaust systems, precise transport timing and placement. Plate C is still stabilizing before after 0 0 W1 W2 W3 Avg W1 W2 W3 Avg W1 W2 W3 Avg Plate A Plate B Plate C Plate response errors.

32 32 What we learned from Plasma RF/heat tolerance Arcing resistance Shape/size Contamination Lifetime and reliability

33 33 Killer Plasma Apps Temperature monitoring Automatic Calibration/Diagnosis??? Equipment Compatibility Power Range RF Tolerance Chemistry Contamination Arcing Tolerance

34 34 Outline Historical perspective Hardware and software applications Breakthroughs that have yet to be realized Distributed control and diagnostics Hardware requirements

35 35 The limitations Shape, Size and Weight Surface mount electronics min ~2mm Needs thin film wafer interconnect to achieve ~10µm flatness Integrated (in Si) electronics still prohibitive for a consumable product Lifetime Battery Films (Plasma, CMP) Performance Envelope Battery up to 200 o C Electronics up to 300 o C

36 36 Shape Size and Weight Zero Footprint Wafer Data Transmission Dielectric Layer as Optical Window Photo-/RF Transmitter Metrology wafer to monitor and map optical reflectance and interference of surface layers Prototyping a zero-footprint optical metrology wafer for real-time monitoring of dielectric film deposition/etching, resist curing/development and metal etch end-pointing Si Battery Professor Nathan Cheung and Students Data Acquisition Unit 500µm

37 37 Batteries Lifetime Button cell secondary commercial solutions not available above 80 o C. Primary solutions are a bit bulky but can go up to 140 o C. Lithium-based thin film technologies still immature, not focused on high temp applications. Temporary solution: screen commercial batteries, make them field replaceable (160 o C ceiling, 10s of hours of operation) Long term solution: wait for high temperature cathode thin film batteries (~200 o C ceiling, 100s of hours) Films Inherent Limitation in Etch just make it thick and provide visible thread wear marks. Might be replaceable in CMP

38 38 Performance Envelope High Temperature Electronics Off the shelf electronics (surface mount or hybrid) ~ 180 o C. Off the shelf electronics with custom clocking ~240 o C. High Temperature Batteries will probably not happen above 200 o C Parasitic power sources / caps

39 39 Expanding Aerial Image Chemical Mechanical Planarization Wet processing Ion Beam PVD CVD RTP??? Automatic Deployment

40 40 Aerial Image Sensor Concept Data acquisition process: Aperture Mask Photodetector High spatial frequency aerial image Aperture mask transmission ( m + n) P + x x Low spatial frequency detector signal

41 41 Choosing Aperture Width & Thickness (cont.) Near-Field Simulation: ( m+ n) P+ x x Illumination phase shift o o Aperture groups phase moving at max min position

42 42 Outline Historical perspective Hardware and software applications Breakthroughs that have yet to be realized Distributed control and diagnostics Hardware requirements

43 PA Bake Spin Exposure HMDS PEB Thin Thin Film Film FB/FF FB/FF Control Control Develop PD Bake 43 Pattern Transfer Control Aerial Image Temperature Etch Feed-forward control control Poly Etch Etch System Temperature, Temperature, Plasma Plasma Voltage, Voltage, Ion Ion Current Current FF/FB FF/FB Control, Control, chuck chuck diagnostics diagnostics Etch Scatterometry Feedback Control Photoresist Removal Scatterometry FB/FF Control Scatterometry Profile Inversion Feedback Control Electrical Testing

44 44 Outline Historical perspective Hardware and software applications Breakthroughs that have yet to be realized Distributed control and diagnostics Hardware requirements

45 45 Automatic Deployment Wireless Wafers must resemble real wafers as much as possible. In a 300mm factory, they must reside in FOUPs and move around via overhead transport. Deployment, data collection, analysis and resulting actions must be automated.

46 46 Batteries! Other Breakthroughs Needed Or, maybe, parasitic power sources full-wafer gate cap is 2 orders of magnitude too small RF pickup coils in plasma have almost unlimited power High temperature electronics! Silicon Carbide Devices about 250 o C Or, maybe thermal isolation for limited time

47 47 Conclusion Wireless Semiconductors Metrology has gone a long way since we started in 1998 Three vendors Officially Adopted by Fabs and Tool Makers Best Known Method (BKM) in several applications Target processes remain in Lithography and Etch, but others are not too far behind Next generation of zero footprint metrology is likely to expand the application base even more