Unlike other types of semiconductor devices, power devices are used
in high voltage applications. So, the deivices is made from a high
tension proof silicon with high thermostability. The high tension
proof silicon is formed by growing an epitaxial layer over silicon
substrate and the substrate is thinned to improve its heat radiation
performance. Rokko plays an important role in the wafer thinning
process though its backside grinding services. The company has well
developed technologies and process recipes to guarantee original
quality of customer products during and after grinding. For instance,
Rokko is able to use a special grinding wheel that stimulates growth
of a gettering layer on grinded surface.
In a power device, an electric current flows in vertical direction
(top to bottom). Because of its characteristics, a power device
has electric poles on its backside to have a stream of electric
current on front. The backside poles are formed through a metal
deposition. In the deposition, a metal layer must grow uniformly
or the bonding surface will start to come off (Air penetration
causes temperature deviation). Therefore, the process requires
a mirror finish rather than a stress relief normal polished surface.
To comply with this technical requirement, Rokko is capable of
providing mirror polished products that precisely meet customer’s
standards through well-developed mirroring technologies.
Rokko has its strength in providing an integrated processing
service.
(Grinding → Polishing → RCA cleaning)
■ Tools and Equipment
Visual inspection
Fully automated grinding
machine
Wafers are inspected at receiving, after taping and polishing.
Grinds wafers of 4 to 8” diameter precisely without influencing
its flatness.
Single-wafer system polishing
machine
Wafer mounting
Wafers are polished according to customer’s thickness requirements.
Wafers are mounted on a ceramic plate.
Batch system polishing
machine
Wafer demounting
Polishes 4 to 8” wafers for mirroring.
Wafers are demounted from a plate after polishing.
RCA cleaning
Final inspection
Wafers are cleaned to remove particles and metal contaminations
after polishing.
Wafers are measured and inspected to comply with customer’s
specifications.
