Flip Chip Solder Bump Characterization in 3D with X-Ray Microscopy. J. Gelb, A. Gu, L. Hunter, B. Johnson, and W.

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1 Flip Chip Solder Bump Characterization in 3D with X-Ray Microscopy J. Gelb, A. Gu, L. Hunter, B. Johnson, and W. Yun July 11, 2012

2 3D X-Ray Microscopy (XRM) Integrated Circuit Sample 3D XRM Data Set 1 Semicon West: July 11, 2012

3 Virtual Cross Sections for Physical Analysis Virtual cross sections of 3D images are a valuable tool for physical analysis 2 Semicon West: July 11, 2012

4 Agenda Packaging Challenges Xradia Overview Flip Chip Solder Bump Case Study Summary 3 Semicon West: July 11, 2012

5 The Typical FA Lab Workflow Non-Destructive Isolation of Failure Failure Confirmation Location Destructive Determination of Failure Cause LSI Tester AC and DC Characteristics Electric evaluation jig 2D X-Ray Scanning Acoustic Microscope Lock-In Thermography Time Delay Reflectometry (TDR) Emission Microscope IR-OBIRCH SEM Microprobe Mechanical Cross Section FIB SEM Decapsulation EDX Auger Challenges: Package complexity increasing Existing non-destructive methods lack resolution Destructive techniques provide resolution but don t allow subsequent testing FA getting more difficult 4 Semicon West: July 11, 2012

6 Typical FA Lab Workflow Non-Destructive Isolation of Failure Failure Confirmation Location LSI Tester AC and DC Characteristics Electric evaluation jig 2D X-Ray Scanning Acoustic Xradia Microscope Microscope XRM Lock-In Thermography Time Delay Reflectometry (TDR) Emission Microscope IR-OBIRCH SEM Microprobe Destructive Determination of Failure Cause Mechanical Cross Section FIB SEM Decapsulation EDX Auger Where XRM Fits Isolating failure location Refined failure information Higher success rate with mechanical cross section XRM may also be used in 2D X-ray inspection mode to locate failure Failure Cause Determination Often, cause may be determined from 3D image without mechanical cross section Time dependent, 4D, reliability studies 5 Semicon West: July 11, 2012

7 Semi FA Example: Electro Migration Related Failure SAM VersaXRM SEM X-section Sample Destroyed Non-Destructive XRM is ideal for finding optimal location for physical cross section Source: Applications of 3D X-Ray Microscopy for Advanced Package Development, K. Fahey, R. Estrada (Xradia), L. Mirkarimi, R. Katkar, D. Buckminster and M. Huynh, Tessera Technologies, Inc, IMAPS Long Beach Semicon West: July 11, 2012

8 Agenda - 3D X-ray Microscopy Packaging Challenges Xradia Overview Flip Chip Solder Bump Case Study Summary 7 Semicon West: July 11, 2012

9 Xradia Inc. Pioneer in Ultra-high Resolution 3D X-ray Microscopy Founded in 2000 HQ in Pleasanton, CA U.S. manufacturer shipping worldwide Privately held Comprehensive market focus From Synchrotron largest installed base of synchrotron 3D microscopes To Research and Industry Labs Highest performance X-ray microscopes for: Electronics Materials Science Geosciences Life Sciences 8 Semicon West: July 11, 2012

10 Synchrotron Capabilities within the Laboratory VersaXRM Family UltraXRM-L200 MicroXCT-200 VersaXRM-500 MicroXCT-400 Resolution mm 50 µm 0.5 µm 150 nm 50 nm Synchrotron micro XRM nano XRM beamline Technology developed for synchrotrons...extended to the lab 9 Semicon West: July 11, 2012

11 Micro CT vs X-ray Microscopy Technology Comparison Traditional Projection based Micro CT How Geometric Mag Works GeoMag = (Dss + Dds) Dss Source Detector Resolution depends exclusively upon geometric Geometric Mag magnification D ss Source: Computed Tomography Willi A. Kalender 2 nd revised edition, 2005 Wiley-VCH Publishing D ds Resolution Highest resolution limited to < 1mm samples Source Detector Contrast Working Distance Difficulty discerning low contrast samples Res. degrades as samples get bigger Sample center of rotation Resolution falls off linearly as the sample moves away from the source 10 Semicon West: July 11, 2012

12 Micro CT vs X-ray Microscopy Technology Comparison Traditional Projection based Micro CT Xradia X-Ray Microscopy Source Detector Resolution depends exclusively upon geometric Geometric Mag magnification Source Geometric mag Detector Optical Mag Scintillator Optical mag Resolution Highest resolution limited to < 1mm samples High resolution maintained for samples as large as 50 mm Contrast Difficulty discerning low contrast samples Phase enhanced contrast detector enables excellent imaging of low contrast samples Working Distance Res. degrades as samples get bigger Resolution is maintained, even for larger samples 11 Semicon West: July 11, 2012

13 Resolution (µm) Low Res XRM Maintains High Resolution at Large Working Distances Geometric Mag Based MicroCTs Resolution rapidly degrades with increasing sample size Substantial difference in resolution as sample size increases VersaXRM High Res Working Distance (mm) Source to center of sample rotation 12 Semicon West: July 11, 2012

14 Micro CT vs X-ray Microscopy Technology Comparison MicroCT X-Ray Microscopy 13 Semicon West: July 11, 2012

15 Agenda - 3D X-ray Microscopy Packaging Challenges Xradia Overview Flip Chip Solder Bump Case Study Summary 14 Semicon West: July 11, 2012

16 Flip Chip Solder Bump Voiding problems Voiding may lead to the formation and/or propagation of cracks Voids local stress gradients in bump microstructure Localized heating and electromigration may occur in solder bumps with voids, due to current crowding effects Voids localized lowered resistance 3D XRM segmentation of voids (red) in solder bumps SEM micrograph. Source: prioritylabs.com 15 Semicon West: July 11, 2012

17 X-ray microscopy on flip chip die Exposure times ranging from 15 minutes to 6 hours are used to image a flip chip die in 3D. Solder bump visualization Voids are automatically assigned to each bump 16 Semicon West: July 11, 2012

18 X-ray microscopy on flip chip die Virtually extract and examine individual bumps for voids Individual bumps may be inspected as needed.through virtual extraction Voids color-coded based on volume (red = large, blue = small) 17 Semicon West: July 11, 2012

19 Number of Occurrences Number of Occurrences Automated analysis After virtual void extraction, automated analysis routines may be run, providing a detailed report about the bump and void distribution (and morphology). 25 Bump Size Distribution 25 Void Fraction Distribution x Bump Volume (µm 3 ) Void Volume Fraction Per Bump (%) In this example, the average bump volume is calculated to be µm 3 and the average void volume fraction per bump is 1.14%. 18 Semicon West: July 11,

20 Agenda - 3D X-ray Microscopy Packaging Challenges Xradia Overview Flip Chip Solder Bump Case Study Summary 19 Semicon West: July 11, 2012

21 Summary X-ray microscopy (XRM) is a powerful technique for the characterization of voids within electronic boards and packages, synergistic with existing FA techniques and leading to increased productivity. The Xradia approach to X-ray microscopy marks a departure from traditional micro-ct, enabling new metrology techniques for present and future FA needs. As applied to flip chip void characterization, large arrays of solder bumps may be inspected and statistical analysis performed on the voiding; individual bumps may be virtually extracted and analyzed prior to destructive cross-sectioning. 20 Semicon West: July 11, 2012

22 Thank you for your attention!