3D Interconnects: Applying X-ray Microscopy as a Void Inspection Technique of Through Silicon Vias (TSVs)

Size: px

Start display at page:

Download "3D Interconnects: Applying X-ray Microscopy as a Void Inspection Technique of Through Silicon Vias (TSVs)"

Brooke George
6 years ago
Views:

1 3D Interconnects: Applying X-ray Microscopy as a Void Inspection Technique of Through Silicon Vias (TSVs) LayWai Kong Advisor: Prof. Alain Diebold College of Nanoscale Science and Engineering at Albany 07/14/2010

2 8keV Lab Based X ray X Microscope Specimen X ray Source Camera Condenser Fresnel Zone Plate Sample stage

3 What are the advantages? cnse.albany.edu No physical cross sectioning into TSVs 3D structural information with computed tomography Good contrast for different materials Minimal sample preparation

Sample Preparation Step1) ~5mm ~5mm 775μm - Area of interest is cleaved to ~ 25mm² Step2) Polishing holder ~25mm 2 sample - The ~25mm 2 sample is then turned up side down and

4 Sample Preparation Step1) ~5mm ~5mm 775μm - Area of interest is cleaved to ~ 25mm² Step2) Polishing holder ~25mm 2 sample - The ~25mm 2 sample is then turned up side down and attached at a polishing holder. Step3) - Using die level polishing method : - The ~25mm 2 sample is polished manually on diamond sand paper from 775 μm to ~100 μm thick. Diamond sand paper

Sample Preparation cnse.albany.edu Step4) Dimple Grinder - Continue polishing to about <50μm with Dimple Grinder - Dimpling is also the method used to prepare the sample for TEM and EBSD.

5 Sample Preparation cnse.albany.edu Step4) Dimple Grinder - Continue polishing to about <50μm with Dimple Grinder - Dimpling is also the method used to prepare the sample for TEM and EBSD. - SiC of diamond paste(particle size:1μm) is apply on the dimpling wheel. Finally) - The 3D(left) and side view(right) of the sample after dimpling - TSVs sit in <50 μm thick remaining silicon. <50 μm

6 What are the advantages? cnse.albany.edu No physical cross sectioning into TSVs 3D structural information with computed tomography Good contrast for different materials Minimal sample preparation Large penetration depth

7 X ray Transmission X ray direction ~50 μm I I o e x 5μm ~30 μm I = The transmitted intensity Io =The initial intensity of photons μ = Attenuation coefficient x = Thickness of material Material Density (g/cm 3 ) TSV Absorption Length (μm) Transmission(%) 50μm 30μm 5μm Silicon Copper

8 What are the advantages? cnse.albany.edu No physical cross sectioning into TSVs 3D structural information with computed tomography Good contrast for different materials Minimal sample preparation Large X-ray penetration depth Nanometer resolution: - ~ 50nm (FOV: 15μm) - ~ 150nm (FOV: 60μm)

8keV X ray Sample (4 μm TSV) Zone Plate ΔRn Camera Diameter: 4 μm

9 Fresnel Zone Plate My super power can t see the void and TSV that they claimed. I Should have installed the Zone Plate. 8keV X ray Sample (4 μm TSV) Zone Plate ΔRn Camera Diameter: 4 μm Depth: 25 μm Rayleigh resolution δ is a function of the outermost Zone width δ = 1.22ΔRn

10 What we can do?!! Inspect changes in voids induced by different annealing conditions keV X ray +70 Camera Sample A (Cu plating) Scan before and after annealing Inspect the change of the void(s). Sample B (Cu Plating + CMP + Anneal)

11 Sample A Sample A (Round TSV) Profile (Cu plating) Annealing conditions 225 C 300 C Contrast Brightness increase Air Si Cu

12 Sample A XY plane of 4μm round TSVs. Incomplete filled at the bottom of TSVs. XY plane of 5μm round TSVs. Void is found at the bottom of TSVs.

13 Sample A 2D Video Y X Videos show a series of 2D images at YZ plane. 4μm 5μm Video A: 4μm TSV Video B: 5μm TSV

14 Sample A 3D Video Video show the 3D tomography of 4μm and 5μm TSVs.

15 5um TSV Sample A (Round TSV) After 225C Annealing 4um TSV Reference line for top of TSV 27.2 μm After 225C annealing for 24 hrs in pure Nitrogen 29.1 μm 25.6 μm After 225C annealing for 24 hrs in pure Nitrogen 32 μm Reference line for Bottom of TSV Both 4 and 5um TSV show Copper is extruded and with de lamination at the wall.

16 5um TSV Reference line for top of TSV Sample A (Round TSV) After 300C Annealing 4um TSV 26.5 μm After 300C annealing for 24 hrs in pure Nitrogen 27.1 μm 22.7 μm After 300C annealing for 24 hrs in pure Nitrogen 29.7 μm Reference line for Bottom of TSV Both 4 and 5μm TSV show Copper is extruded and with de lamination can be seen at the wall.

17 Sample B Sample B (Round TSV) Profile (Cu Plating + CMP + Annealed to 150C) Further annealing conditions 225 C 300 C Contrast Brightness increase Air Si Cu

2μm After 225C annealing for 24 hrs in pure Nitrogen 25.

18 5μm TSV Reference line for top of TSV Sample B (Round TSV) After 225C Annealing 4μm TSV 26μm After 225C annealing for 24 hrs in pure Nitrogen 26.6μm 25.2μm After 225C annealing for 24 hrs in pure Nitrogen 25.8μm Reference line for Bottom of TSV Both 4 and 5μm TSV show Copper extrusion and voids are induced at the center of TSVs.

19 5μm TSV Reference line for top of TSV Sample B (Round TSV) After 300C Annealing 4μm TSV 26.7μm After 300C annealing for 24 hrs in pure Nitrogen 27.3μm 24.6μm After 300C annealing for 24 hrs in pure Nitrogen 25.8μm Reference line for Bottom of TSV Both 4 and 5μm TSV show Copper extrusion and voids are induced at the center of TSVs.

20 Top Before post anneal Sample B (Round TSV) Void induced after 225C After 225C Observe at different XY plane(1 & 2) 1 TSV Bottom

21 Sample B (Round TSV) Extrusion after 300C Gold particle (1 2μm) Before post anneal After 300C

22 Summary Lab-based X-ray microscope is currently the most powerful method for void inspection in TSV without physically cross sectioning into the TSV (compare with TEM and FIB). Change of void, voids induced and extrusion are clearly seen after different annealing conditions without physically cross sectioning the TSVs. However, it is currently limited to small sample sizes.

23 Acknowledgement Andy Rudack Raymond Caramto Ehrenfried Zschech Peter Krueger Yvonne Ritz James Lloyd

24 Thank You cnse.albany.edu

Transzmissziós és pásztázó elektronmikroszkópos minták készítése ionsugaras vékonyítással

Transzmissziós és pásztázó elektronmikroszkópos minták készítése ionsugaras vékonyítással Radi Zsolt Technoorg Linda Kft., Budapest Oktatói és Doktorandusz Konferencia Visegrád, 2012 State-of-the-art materials