IR-SWLI for subsurface imaging of large MEMS structures

LED based infrared scanning white light interferometry (IR-SWLI) permits non-destructive imaging of embedded MEMS structures. We built an IR-SWLI instrument featuring a custom-built IR-range LED-based light source, capable of stroboscopic use. The source combines multiple separately controllable LEDs with different wavelengths into a collimated homogenous beam offering an adjustable spectrum. We employ software-based image stitching to form millimeter-size 3D images from multiple high magnification scans. These images delineate three layers in a MEMS cavity covered by silicon and reveal a micron-size inlet inside the channel.