New method monitors semiconductor etching as it happens – with light

University of Illinois researchers have a new low-cost method to carve delicate features onto semiconductor wafers using light – and watch as it happens.

''You can use light to image the topography and you can use light to sculpture the topography,'' said electrical and computer engineering professor Gabriel Popescu. ''It could change the future of semiconductor etching.''

Chip makers and semiconductor researchers need to very precisely control the dimensions of their devices. The dimensions of the components affect performance, speed, error rate and time to failure.

Semiconductors are commonly shaped by etching with chemicals. Etching errors, such as residual layers, can affect the ability to further process and etch as well as hamper device performance. Thus, researchers use time-consuming and costly processes to ensure precise etching – for some applications, to within a scant few nanometers.

The Illinois researchers' new technique can monitor a semiconductor's surface as it is etched, in real time, with nanometer resolution. It uses a special type of microscope that uses two beams of light to very precisely measure topography.

''The idea is that the height of the structure can be determined as the light reflects off the different surfaces,'' said electrical and computer engineering professor Lynford Goddard, who co-led the group with Popescu. ''Looking at the change in height, you figure out the etch rate. What this allows us to do is monitor it while it's etching. It allows us to figure out the etch rate both across time and across space, because we can determine the rate at every location within the semiconductor wafer that's in our field of view.''