JVD™ Solder Advantages

 

For solder and ancillary metal deposition, the JVD approach, jet sources, and relative motion schemes provide many benefits.

 

WIDE RANGE OF SOLDERS

These include AuSn 80/20 and some off-eutectics, 78/22, 75/25, 73/27;  In, InSn, SnAg, SnCu, SnCuAg, SnInAg -- virtually every solder used in microelectronics.

ADHESION/BARRIER METALS

Ti, Cr, Ta, Ni, TiPtAu, TiW, TiNiAu

RELATED METALS

Cu, Au, Ag, Sn, Al, Cr, Ni, Ti, Ta

SUBSTRATE MATERIALS

Virtually any substrate, since JVD is a "low vacuum" approach

SUBSTRATE SIZE

Wafers 2", 3", 4", 6", 8";  Square from 2"x2" to 6"x6" and rectangular substrates, down to small heatsinks of millimeter dimension

SINGLE WAFER PROCESSES

2" to 8" diameter or multiple substrates fitting into those areas

BATCH PROCESSES

4" wafers or 4"x4" batches of 10.  Smaller substrates in batches up to 20 per run.  Small heatsinks such as CuW, MoW, as many as hundreds per run in appropriate holders.

THICKNESS RANGE

All solders, 1 to 20 microns;  adhesion/diffusion layers, typically 1,000 to 2,500 Å

HIGH DEPOSITION RATES

5 microns on a 6" wafer in 20 minutes for all solders.  The "high" pressure of JVD implies high metal atoms concentration in jet;  therefore, high deposition rates.

ALLOY DEPOSITION

Alloy components deposit together rather than as separate layers.

ACCURATE COMPOSITION

Metal vapor deposited from the jet preserves the starting alloy wire composition.

THICKNESS CONTROL

Plus/minus 2,500 Å out of, e.g., 10 microns across a 6" or 8" wafer.

"ION ETCH" PRE-CLEAN

In situ low ion energy, high density plasma for residual resist removal.  Other in situ pre-clean techniques include RF oxygen plasma and microwave discharge O atom exposure.

MINIMAL MATERIAL WASTE 

Typical capture efficiencies in the jet are ~ 90%.

LOW TEMPERATURE PROCESSING

Fast relative motion of substrate keeps its temperature low because of short residence time in front of "hot" jet source.  Maximum final wafer T of single wafer process is less than 85°C.

PHOTORESIST AND LIFTOFF COMPATIBILITY                        

Low process T avoids thermal damage to photoresist mask.

NANOCLUSTER DEPOSITION

In the nozzle and jet, JVD flow and pressure conditions can be easily modified to promote nucleation, growth, and deposition of nanoclusters at very high rates.  Cluster deposition, which is highly directional, is advantageous for solder bumps, because the high inertia of the accelerated, heavier clusters gives trajectories almost exactly perpendicular to the wafer.  In consequence, there is little shadowing by resist walls, and since sidewall deposition is also reduced, there is reduced breadloafing.  For small windows in the resist, where the aspect ratio is high, hole filling by nanoclusters is extremely efficient.  In recent years, we have been putting this key nanocluster capability of JVD to increasing use in making small bumps in dense arrays.

CLEAN AND GREEN OPERATION

With starting materials of pure metals, there are no toxic precursors or effluents, and high capture efficiency minimizes waste.  Nanocluster mode operation is particularly effective in concentrating the deposit.  For additional information, click on the following link for the 2011 EPA SBIR success story in "Science Matters" newsletter:  www.epa.gov/sites/production/files/2015-06/documents/jetprocess.pdf

COMPACT DEPOSITION CHAMBERS  

The "Index Arm" JVD deposition tool in Figure 7 deploys JVD's solder deposition capabilities in a particularly concentrated form.  Four different jet sources, for example, AuSn, Ti, Pt and Au are arranged in a circle, and the "index arm" permits a spinning wafer to visit and "scan" each source in turn to build up a complete layer. The ion etch pre-clean is integrated into the AuSn jet source.  The entire chamber is ~ 16 liters (23" diameter, 6 inches high).