Armstrong Optical and its supplier Precitec Optronik have recently investigated the measurement of blind vias in silicon wafers. The vias were produced by laser drilling and had external hole diameters of between 15 and 30µm and depths ranging from 50 to 500µm.
By using the CHRocodile IT sensor system it was possible to measure both the external hole diameters and the depths of the blind vias, simultaneously, in a non-contact fashion with high accuracies.
The CHRocodile IT sensor system is one of a family of instruments available from Precitec Optronik that use the chromatic confocal sensor approach – the optical source being a broad spectral output device.
As the sensor probe is passive - having no power or electrical connection and at the end of an optical fibre that can be 30m in length - it is ideal for integration into production environments. The CHRocodile IT system operates at a 4KHz data collection rate and has been used to perform non-contact measurement tasks on silicon and GaAs wafers during grinding and on PV cells during manufacture.