Die / Wafer Thinning:

R3 offers mechanical and chemical means of thinning silicon die and wafers to thickness as low as 15-25 microns (1 mil) for the purposes of volume reduction in critical form factor systems.  For die processing, bare die are precisely transferred to a 150mm (6 inch) carrier wafer to enable economies of scale by permitting the thinning of dozens or hundreds of die simultaneously.  Die are bonded to the carrier by using an acrylic-based spin-on polymer.  The initial thinning process is performed by a mechanical grinding operation.  In order to reduce chipping defects on the die, the gaps between bare die are filled with a temporary thermoplastic material.  The mechanical grinding stops short of the final die thickness by 10 microns to allow for precision final thinning, minimization of sub-surface crystalline damage, and enhanced surface finish that enables covalent bonding and enhanced thermal contact between interfaces.

The final thinning process utilizes Chemical Mechanical Planarization (CMP) to slowly polish the die.  This process simultaneously removes the gap filling thermoplastic material.  The final total thickness variation (TTV) for this thinning process is specified to be less than 1 micron.  After thinning, the entire wafer of die can be transferred to a permanent structure for applications like 3DI, or alternatively the handle wafer can be diced into individual die to preserve a rigid backing for handling of the thinned components until the time of use.  Once mounted, the thinned components are released using either thermal or chemical processes to remove the spin-on adhesive material.

The same process steps can be used to thin entire wafers up to 150mm with far less processing overhead.  A carrier wafer with spin-on acrylic bonding is still used to ensure proper handling during the thinning process.