Grooved-Membrane Head Function
The grooved-membrane head is used to polish silicon semiconductor
wafers on a rotary lapper machine. Wafers are quickly attached to the
flexible membrane with vacuum, using shallow grooves on the flat
surface of the membrane. The rotating head positions the wafers in
abrading contact with rotating fixed-abrasive discs that are attached to
the precision-flat rotating platen.
Micron-Sized Abrasive Particles
Small abrasive particles having selected sizes of 3 micron or smaller
can be chosen from a wide range of abrasive materials to uniformly
remove nanometer amounts of material from the polished silicon wafers.
Rigid Retainer Ring Eliminated
The rigid retainer ring used on conventional membrane-type wafer polishing heads is eliminated. Instead of capturing the wafer within the rotating retainer ring, the wafer is attached to the flexible membrane with vacuum. The membrane is held in place on the head to resist lateral friction type abrading forces by an annular system of pins that slide vertically in matching pin-hole receptacles in the head. The flexible elastomeric membrane “floats” in a vertical direction while controlled abrading pressure is applied uniformly across the full abraded surface of the wafer.
High Speed Wafer Polishing
Abrasive discs having abrasive coated islands allow a large increase in the abrading speeds of the wafers. These water mist cooled fixed-abrasive discs can be operated at much higher abrading speeds than conventional liquid abrasive slurry abrading systems. The disc islands prevent hydroplaning of the wafers at the high abrading speeds.
Multiple Pressure Chamber Head
Multiple annular pressure chambers in the head can provide different abrading pressures in different portions of the flexible elastomer membrane. These independent pressure chambers allow the amount of material removed from selected portions of a wafer to be controlled by simply adjusting the abrading air pressure supplied to each chamber.
Use with CMP Slurry Pads
The grooved-membrane heads can also be used with resilient chemical mechanical planarization (CMP) pads and liquid abrasive slurries to polish silicon wafers.
Retrofit Grooved -Membrane Heads
These grooved-membrane heads can be retrofitted on the many conventional flexible membrane wafer polishing heads that are in widely used today. These relatively inexpensive heads can provide superior performance at any abrading speeds.