Formfactor, Inc. · NASDAQ:FORM
Formfactor — Technical Presentation (June 2015)
40 slides from Formfactor's technical presentation, June 2015
Slide 1: Minimizing Parametric Probe Card Stray Capacitance
Minimizing Parametric Probe Card Stray Capacitance Larry Levy & Edwin Soler FormFactor Inc & GLOBALFOUNDRIES
Slide 2: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 2
Slide 3: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 3
Slide 4: Stray Capacitance Definition
Stray Capacitance Definition • Stray capacitance is unintended and unwanted capacitance in a circuit. • Capacitance doesn't exist only within capacitors. In fact, any two surfaces at different electric potential, and that are close enough together to generate an electric field have capacitance (Wiki
Slide 5: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 5
Slide 6: Why is Stray Capacitance Important for Parametric Testing?
Why is Stray Capacitance Important for Parametric Testing? • Capacitance is used for process monitoring in some tests Example : Critical Capacitance measurement example , signature measurement of the technology Classic measurement lpoly = length of poly = capacitance of poly finger capacitance of la
Slide 7: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 7
Slide 8: Background
Background ▪ Why lower capacitance became more important? – For Case Study Customer A Back door capacitance some pads are tied together in the wafer – In the case of GLOBALFOUNDRIES it was a desire to more closely match or improve on the existing technology 8
Slide 9: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 9
Slide 10: Engineering Stray Capacitance Measurement Method
Engineering Stray Capacitance Measurement Method • Agilent E4980A Very important to have an engineering capability that correlates to testers in the field 10
Slide 11: Capacitance of Probe Card Components
Capacitance of Probe Card Components Interchangeable Platform Adds Complexity Probe Card Mother Board Interchangeable Insert Unit 1XN Common inserts for Multiple Tester Platforms Multiple spring US Patent Nos. 7,498,825 types available and 7,898,242 11
Slide 12: Probe Card Stray Capacitance
Probe Card Stray Capacitance • Traditionally stray capacitance is measured from pin to pin in air and on the wafer Pin 1 Pin 2 Pin 3 Customarily pins have been designed to come from opposite sides for course pitch/larger pads Pin 1 Pin2 For tight pitch and small pads it is becoming more common f
Slide 13: Prober Card Break Down
Prober Card Break Down • 25 pin 80um pitch design Probes Single (Beam pitch Narrow) Dual (Beam pitch Wide) 63~89 fF 19~43 fF 7~32 fF +15~41 fF 63~89 fF 19~43 fF Beam to Beam clearance has the largest impact 13
Slide 14: Probe Card Break Down Interchangeable Insert Unit
Probe Card Break Down Interchangeable Insert Unit Max 682 fF Average 87.9 fF 14
Slide 15: Probe Card Break Down Mother Board
Probe Card Break Down Mother Board Max 300 fF Average 37.9 fF 15
Slide 16: Full Probe Card of Stray Capacitance
Full Probe Card of Stray Capacitance 25pin, 80um pitch,Single Direction Using Standard Design Rules Max 980 fF Average 126 fF 16
Slide 17: Stray Capacitance Probe Card Component Summary
Stray Capacitance Probe Card Component Summary • Components – Probes have minor contribution – Focus on MB – Focus on Insert • Experimental Inserts were designed with both dual and single direction as well as a new MB – Redesigned to minimize capacitance and tighten distribution • Keeping the goal o
Slide 18: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 18
Slide 19: Case Study Customer A Problem Statement
Case Study Customer A Problem Statement Outliers are pads tied together in the wafer FFI MEMS Outliers Bars measured with both card types Cantilever
Slide 20: Original Full Probe Card of Stray Capacitance
Original Full Probe Card of Stray Capacitance Using Standard Design Rules (25pin, Single Direction) Max 980 fF 11 vs 12 85 fF Average 126 fF 10+11 vs 12+13 1288 fF 10+11 vs 12+13+14 1351 fF 20
Slide 21: Probe Card Break Down Interchangeable Insert Unit
Probe Card Break Down Interchangeable Insert Unit Max 682 fF 11 vs 12 85 fF Max 105 fF 11 vs 12 68 fF Average 87.9 fF 10+11 vs 12+13 812 fF Average 10 fF 10+11 vs 12+13 164 fF 10+11 vs 12+13+14 875 fF 10+11 vs 12+13+14 164 fF 21
Slide 22: Probe Card Break Down Mother Board
Probe Card Break Down Mother Board *Max was not improved much due to cost restrictions (3 higher capacitance) * * * Max 300 fF 11 vs 12 0 fF Max 297 fF 11 vs 12 0 fF Average 37.9 fF 10+11 vs 12+13 476 fF Average 6.18 fF 10+11 vs 12+13 34 fF 10+11 vs 12+13+14 476 fF 10+11 vs 12+13+14 34 fF 22
Slide 23: Full Probe Card of Stray Capacitance
Full Probe Card of Stray Capacitance Improved Design Rule(25pin, Single Direction) Max 335 fF 11 vs 12 68 fF Average 16 fF 10+11 vs 12+13 198 fF 10+11 vs 12+13+14 198 fF 23
Slide 24: Full Probe Card of Stray Capacitance
Full Probe Card of Stray Capacitance Improved Design Rule(25pin, Dual Direction) Max 295 fF 11 vs 12 18 fF Average 11.8 fF 10+11 vs 12+13 121 fF 10+11 vs 12+13+14 172 fF 24
Slide 25: Case Study Customer A Summary
Case Study Customer A Summary • We were able to drastically reduce full card stray capacitance – Although the bridged probes still demonstrated higher capacitance, they were now within acceptable limits Dual Single Stray Capacitance (unit:fF) Measurement: Open circuit Sample Cantilever TK5613B TV1 T
Slide 26: Case Study Customer A Final Results
Case Study Customer A Final Results Standard Design 11 vs 12 85 fF Improved Design 11 vs 12 18 fF 11 vs 12 68 fF 26
Slide 27: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 27
Slide 28: GLOBALFOUNDRIES Quality Policy
GLOBALFOUNDRIES Quality Policy Quality is a way of life GLOBALFOUNDRIES will exceed our customers' expectations through the dedication and continuous improvement efforts of our employees. To do so, our employees embrace and adhere to the following principles: •Customer First We are committed to best
Slide 29: GLOBALFOUNDRIES Problem Statement
GLOBALFOUNDRIES Problem Statement • Standard FFI MEMS card has higher capacitance FFI MEMS Outliers FFI MEMS Outliers Other supplier 25 Pin Design 2 Cards Each Run Twice No Pads Bridged together 29
Slide 30: 22 Pin Single Direction Redesigned Measured at FormFactor
22 Pin Single Direction Redesigned Measured at FormFactor 25 Pin redesign Redesigned 22 and 25 pin results very similar 30
Slide 31: GLOBALFOUNDRIES Evaluation
GLOBALFOUNDRIES Evaluation • GF does testing/qualifications at different frequencies during probe card validation – Different devices have different capacitance/conductance ranges • Industry standard Capacitance and Conductance are (Test Freq): 1 fF to 1.2 nF and 10 nS to 7.5 mS (1 MHz) 1 fF to 10 n
Slide 32: Capacitance Comparison-Frequency 1 KHz
Capacitance Comparison-Frequency 1 KHz 22 pin Card 22 pin Card (Standard Design vs Other Supplier) (Standard Design vs Improved Design) Other Supplier FFI Other Supplier FFI Improved Measured with 25 channel tester 32
Slide 33: Capacitance Comparison-Frequency 10 KHz
Capacitance Comparison-Frequency 10 KHz 22 pin Card 22 pin Card (Standard Design vs Other Supplier) (Standard Design vs Improved Design) Other Supplier FFI Other Supplier FFI Improved Measured with 25 channel tester 33
Slide 34: Capacitance Comparison-Frequency 100 KHz
Capacitance Comparison-Frequency 100 KHz 22 pin Card 22 pin Card (Standard Design vs Other Supplier) (Standard Design vs Improved Design) Other Supplier FFI Other Supplier FFI Improved Measured with 25 channel tester 34
Slide 35: Capacitance Comparison-Frequency 1 MHz
Capacitance Comparison-Frequency 1 MHz 22 pin Card 22 pin Card (Standard Design vs Other Supplier) (Standard Design vs Improved Design) FFI Other Supplier Other Supplier FFI Improved Measured with 25 channel tester 2x card shows same chart 35
Slide 36: 1 MHz Plot Shows Improvement in Range and Distribution
1 MHz Plot Shows Improvement in Range and Distribution
Slide 37: Overview
Overview • Definition Of Capacitance • Importance of Minimizing Capacitance • Background • Capacitance of Probe Card Components • Case Study Customer A • GLOBALFOUNDRIES Case Study • Summary 37
Slide 38: Stray Capacitance Summary
Stray Capacitance Summary • Prior to doing parametric test a procedure is usually performed to null out the capacitance produced by the tester and probe card. Despite this effort, uncompensated probe card and tester stray capacitance can still be a problem • The uncompensated stray capacitance can/d
Slide 39: Acknowledgements
Acknowledgements • IBM – Jack Cassels, Ron Feroli, Lou Medina • GLOBALFOUNDRIES – Alan Romriel, Edwin Soler, Ronie Geronimo, Jackie Ngo-Hatchie, Carrie Demers • Keysight Technologies – Goto-san • FFI Japan – Yoshida-san, Kawamata –san 39
Slide 40: Thank You
Author Thank You 25TH ANNIVERSARY June 7-10, 2015 2-0-1-5 SW Test Workshop 40