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KGD Probing of TSVs at 40 um Array Pitch

KGD Probing of TSVs at 40 um Array Pitch . 3D-TSV Probe Technology Goals MEMS probe tip evolution Contact performance TSV pad damage (or lack thereof) Conclusions. Ken Smith, Peter Hanaway, Mike Jolley, Reed Gleason, Chris Fournier, and Eric Strid. 3D-TSV Probe Technology Development Goals.

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KGD Probing of TSVs at 40 um Array Pitch

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  1. KGD Probing of TSVs at 40 um Array Pitch • 3D-TSV Probe Technology Goals • MEMS probe tip evolution • Contact performance • TSV pad damage (or lack thereof) • Conclusions Ken Smith, Peter Hanaway, Mike Jolley, Reed Gleason, Chris Fournier, and Eric Strid

  2. 3D-TSV Probe Technology Development Goals • Scale array pitch to 40 um • Reduce pad damage to allow prebond probe • Decrease cost of test • Simplified, high yield process • Fundamental understanding and accurate models of contact performance

  3. RF filters, switches Process monitors (including M1 copper) RFSOC Multi-DUT Pyramid Probe Technology

  4. 3D Probing Requires a New Cost Structure Technology must be printed, repairable, scalable, compliant Constant cost per area DRAM & Flash Vertical probe: cost increases with density Logic/SoC 4 2 3D Requires constant cost per chip COGS/ pin ($) in 2012 1 Printed probe: nearly constant cost per area 0.50 0.25 0.12 Array Pitch (um) 0.06 3 6 1600 400 800 12 25 50 100 200

  5. Scaling a Probe Card • Decrease XYZ dimensions by K • Same materials • Decrease Z motions by K • Force per tip decreases by K2; tip pressure constant 100 um pitch ~10 gm/tip 35 um pitch ~1 gm/tip

  6. Wafer 3D TSV Probe Card Architecture • Pyramid Probe ST: Pads on membrane • Routing limitation ~3-4 rows deep from DUT pad perimeter • Replaceable contact layer PCB PCB Plunger

  7. Replaceable Contact Layer • Tips are 5 um square and 20 um tall • 35 um pitch array • 24 x 48 tips

  8. Contact resistance versus probing force • Single 12 um square tip • Sn plated wafer 5 um thick

  9. Contact resistance versus probing force • 6 um tip • Force required is similar to 12 um tip

  10. Force (gm•f ) vs. Deflection (um) • 1gm•f /um tip design • High durometer elastomer

  11. Force (gm•f ) vs. Deflection (um) • 0.1 gm•f tip design • Low durometer elastomer

  12. Pyramid Probe ST Routing • Unique fine-pitch routing • High-frequency performance similar to Pyramid Probes • Example is memory array • – 50 um x 40 um pad pitch • – 40 x 6 pad array

  13. Fully routed 6x40 array with 40-50 um pitch

  14. Optical photograph of probe mark array • Marks are exceptionally uniform • ~1 gram / contact for low pad damage

  15. Profilometer scan of probe mark array • Maximum depth 100 nm • Maximum berm 500 nm

  16. Probe marks on ENIG TSV pad • Exaggerated conditions: 10 TDs at 2.5 gf • Navigation grid (50 x 40 um) shows 3 probe marks on the 100 um diameter pad

  17. Probe mark depth less than surface roughness (~200 nm)

  18. Probe mark on ENIG pad • ~3 x 7 um • Exposed Ni ~50% • Depends on surface grains

  19. Probe mark uniformity: Profilometer scans • Depth: Mean 68, Stdev 11 • Berm: Mean 363, Stdev 76

  20. TDR traces on open and short • <40 ps rise / fall times (100 ps / div) • Limited by routing density in ST

  21. Conclusions • Practical probe cards are capable of 40 um pitch and tip forces below 1 gm • Pad damage at these low forces is extremely small with scrub marks less than 100 nm deep • Lithographically printed probe cards enable a scalability path to lower cost and finer pitches • Probing the TSVs is not out of the question

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