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

4. 3D Probing Requires a New Cost Structure 4 COGS/ pin ($) in 2012 Array Pitch (um) 400 200100502512 800 631600 2 1 0.50 0.25 0.12 0.06 DRAM & Flash Logic/SoC Constant cost per area Printed probe: nearly constant cost per area Vertical probe: cost increases with density 3D Requires constant cost per chip Technology must be printed, repairable, scalable, compliant

5. Scaling a Probe Card 100 um pitch ~10 gm/tip 35 um pitch ~1 gm/tip Decrease XYZ dimensions by K Same materials Decrease Z motions by K Force per tip decreases by K 2 ; tip pressure constant

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

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 (gmf ) vs. Deflection (um) 1gmf /um tip design High durometer elastomer

11. Force (gmf ) vs. Deflection (um) 0.1 gmf 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