Logitech WBS7 - Procedure for Wax Mounting with bulk Crystalbond Stick

Contributed by Miguel Daal, Mazin Group  -- 2018-04-24

Procedure for wax-mounting a 100mm Silicon wafer to another 100mm silicon carrier wafer, using the Logitech WBS7 Wafer Bonder.

• Cover Hotplate surface with tinfoil, heat hotplate to 150°C.
  • Bay 5 solvent bench is preferred
  • Keep flammable solvents away!
• Place 4" polished handle wafer on hotplate.
• Apply wax to center of carrier wafer only.
  • For mounting a 4-inch wafer, you need a good amount of wax to ensure coverage to wafer edges, eg.2-3mm thick.
  • For 4-inch wafers, We have found that ~2.3 grams of wax is the right amount. Cut a ~1cm chunk off the CrystalBond wax stick with razor, then cut that into 2/3rds, weigh with tared scale in Bay 5.
  • Should produce approximately 2-inch diameter size puddle of crystal bond wax.
  • If you need to adjust the wax amount, you can use a transparent top-substrate to observe whether full coverage is achieved. Few millimeter-sized bubbles typically are acceptable.
• Place the top wafer on the melted wax at this step, and align wafer flats while wax is wet.
• Remove wafers from hotplate and cool on clean napkin (do not let wax stick to surfaces while cooling). Check that wafer flat alignment is good.
• Open Logitech Bonder chamber:
  • Unscrew clamp until higher than clamp arm,
  • Swing front of clamp arm to the left (Difficult to disengage),
  • Lift bonder lid (also takes some force to open - ignore vacuum reading on digital display)
• Place 6" filter paper on the glass plate of the logitech.
• Place wafers on top of the filter paper, on the glass plate of the Logitech bonder.
• Place 6" filter paper on top of the wafers. Wafers shouldhave filter paper on top and bottom to catch excess wax.
• Close and lock Logitech bonder hatch.
• Turn on Logitech bonder power (bottom right of machine chassis)
• On front panel of  Logitech bonder, confirm that Applied Pressure gauge is set to 5 psi.
• Enter the process settings:
  • [setup] -> [Temp]
    • Bonding: 120°C
    • Endpoint: 65°C
    • Offset: 20°C
    • Units: C
  • [setup] -> [Vac Thres]
    • Proceed if Below: 2.4E+01 mBar
    • Abort if Below: 3.2E+01 mBar
  • [setup] -> [Process Control]
    • Process: Heat + Outgas
    • Soak: 5min
    • Bond: 15min
    • O.G. Limit: 20min
    • P.P. del: 1min
  • [Setup] -> [Heads]
    • Head 1 On
• Start Process: [Process] -> [Start]
• Process takes about 45min
  • Unload when it displays Status: Ready
  • It is normal to see wax on the filter paper, indicating full/over-coverage. However you might need to adjust the wax amount to prevent too much wax escaping the wafer and causing too thick a bonding layer. About ~1cm of leaking wax on the filter paper is ideal.
• If wax leaked onto the glass plate: remove glass plate and clean with Acetone+Wipe. The surfaces must be very clean of wax when you're done, or else the lid or wafers may get stuck on the next run.
• Turn off Logitech bonder (bottom right of machine chassis)
  • Close lid and clamp
• Clean excess wax off your wafer using the POLOS Spinners, and an Acetone squirt bottle, followed by ISO & N2 dry (run both sides of the wafer, multiple times if needed).