Automatic wafer sorting

For microelectronics, and other microstructure technologies, crystalline wafers are the most important substrate material. In high-throughput applications like wafer sorting and quality control, the Omega Scan plays its speed advantage.

Omega Scan reflection diffractogram for a c-Sapphire wafer
Stereographic projection of the c-Sapphire wafer main crystalline directions calculated from an Omega Scan measuremen
Warp and bow measument with a line laser instrument attached to the diffractometer
Sapphire wafer surface geometry as the result of the warp and bow measurement

Automatic wafer sorting

About 50000 tons of monocrystalline Silicon are grown each year for the production of wafers. Other semiconductors like Ge and GaAs are used in smaller quantities for special applications like high electron mobility devices. In the recent years, wide-bandgap (WBG) semiconductors like GaN are introduced for a large range of applications in diodes and power semiconductors. This has caused a drastic increase in the production of sapphire wafers, which are used as substrate for thin films of GaN. The crystal growth of III-V compounds like GaN and AlN or the WBG semiconductor SiC is a very complex process due to the fact that it takes place in the gas-solid equilibrium. However the production of wafers of these materials is increasing.

The traditional semiconductors have cubic crystal structures of the close packed type. GaN and AlN crystallize in the hexagonal Wurtzite structure. SiC is known for its polymorphism; most of the polymorph structures are based on Wurtzite. The crystal structure of Sapphire is trigonal R centered.

Solutions

With its high speed and precision, the Omega Scan technique is ideal for sorting applications. We can characterize a wafer by its surface tilt vector and an in-plane direction, for instance the perpendicular of the flat. All that information can be gathered by a single Omega Scan measurement.

For all established wafer materials and orientations, Omega Scan solutions are available. In SiC, it is possible to detect and separate the most common polymorphs, 4H and 6H.

For high-throughput applications like wafer sorting, we offer automated wafer handling using market-available solutions. The instruments' capabilities can be extended by an additional sensor to determine warp and bow of the wafer.