Use of Wafer Applied Underfill for 3D Stacking

2011 ◽  
Vol 2011 (1) ◽  
pp. 000008-000016 ◽  
Author(s):  
Antonio La Manna ◽  
K. J. Rebibis ◽  
C. Gerets ◽  
E. Beyne
Keyword(s):  
Flip Chip ◽  
Solder Bump ◽  
Initial Assessment ◽  
Test Vehicle ◽  
Differential Movement ◽  
The Right ◽  
3D Stacking ◽  
Material Uniformity ◽  
Work Done

A key element for improving 3D stacking reliability is the choice of the right Underfill materials. The Underfill is a specialized adhesive that has the main purposes of locking top and bottom dies; it must fill the gap between bumps and between dies, while reducing the differential movement that would occur during thermal cycling. Traditional underfill processes are based on local dispensing after solder bump reflow (Capillary dispensing), or before flip chip operation with no need of reflow (No Flow Underfill, NUF). In case of 3D stacking, such processes present some limitations: need of a dispensing area (die size increase); material flowing (spacing between dies) and cost (low throughput). After an introduction on typical underfill applications like die-to-package and die-die assembly, we report the work done to assess the properties of several Wafer Applied Underfill (WAUF) materials and their integration in 3D stacking. These materials have been initially applied on silicon wafers in order to assess the minimum achievable thickness and the material uniformity. The wafers have been coated by using different methods: spin coating and film lamination. After this initial assessment, the most promising materials have been used for 3D stacking. The test vehicle used has Cu/Sn μbumps with a pitch of 40μm. The quality of the materials is judged by electrical test, SAM (Surface Acoustic Microscope) and X-SEM (Scanning Electron Microscope).

Material uniformity of CdZnTe grown by low-pressure bridgman

2001 ◽  
Vol 458 (1-2) ◽  
pp. 96-103 ◽  
Author(s):  
C.M. Greaves ◽  
B.A. Brunett ◽  
J.M. Van Scyoc ◽  
T.E. Schlesinger ◽  
R.B. James
Keyword(s):  
Low Pressure ◽  
Material Uniformity

Material uniformity and inhomogeneity in anelastic bodies

1974 ◽  
Vol 53 (3) ◽  
pp. 246-276 ◽  
Author(s):  
C. -C. Wang ◽  
F. Bloom
Keyword(s):  
Material Uniformity

Excimer Laser Crystallisation of Poly-Si TFTs for AMLCDs

2000 ◽  
Vol 621 ◽  
Author(s):  
S D Brotherton ◽  
D J McCulloch ◽  
J P Gowers ◽  
J R Ayres ◽  
C A Fisher ◽  
...  
Keyword(s):  
Laser Energy ◽  
Short Channel ◽  
Circuit Performance ◽  
Fine Grain ◽  
Implantation Damage ◽  
Shot Number ◽  
Drain Field ◽  
Considerable Degradation ◽  
Material Uniformity ◽  
Device Properties

ABSTRACTThere is interest in reducing the shot number in the poly-Si laser crystallisation process in order to improve its throughput. Two distinct shot number dependent effects have been identified, which are both laser intensity dependent. The critical laser energy density is that which causes full film melt-through, and the major issue occurs at energies greater than this, where there is a considerable degradation in device uniformity with reducing shot number. The cause of this is non-uniform recovery of the full-melt-through fine grain poly-Si, and it is demonstrated that by extending the trailing edge of the beam, the material uniformity at reduced shot number can be improved. For energies less than this, the issue is not so much uniformity, as a general degradation in overall device properties with reducing shot number, which has been correlated with reducing grain size.In more demanding, future applications (such as system-on-panel), it will be necessary to improve circuit performance and approach that of current MOSFET devices. This will require short channel, self-aligned (SA) TFTs, and some of the issues with this architecture, particularly lateral ion implantation damage beneath the gate edge and drain field relief are discussed.

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