White light interferometer for high precision wafer inspection
The IMS5420 is a high-performance white light interferometer for non-contact thickness measurement of monocrystalline silicon wafers. The controller has a broadband superluminescent diode (SLED) with a wavelength range of 1,100 nm. This enables the thickness measurement of undoped, doped and highly doped SI wafers with only one measuring system. The IMS5420 achieves a signal stability of less than 1 nm. The thickness can be measured from a distance of 24 mm.
Precise wafer thickness measurement
Due to the optical transparency of silicon wafers in the wavelength range of 1.100 nm, the IMS5420 interferometers can precisely detect the thickness. In this wavelength range, both undoped silicon and doped wafers provide sufficient transparency. Therefore, wafer thicknesses up to 1.05 mm can be detected. The measurable thickness of the air gap is even up to 4 mm.
Precise thickness measurement during lapping
In wafer fabrication, a crystalline silicon ingot is cut into thin slices of about 1 mm. The discs are then ground and lapped to obtain the desired thickness and surface finish. To achieve high process stability, interferoMETERs are used for inline thickness measurement in lapping and grinding machines. Due to its compact design, the sensor can also be integrated in confined installation spaces. The thickness values are used for machine control as well as for quality control of the wafer.