Laser desorption of hydrogen could be boon to silicon-chip makers

Anything that smoothes the process of computer-chip manufacture even just a bit could mean millions of dollars in savings to the chip maker. Now, researchers at the University of Minnesota (Minneapolis, MN), Vanderbilt University (Nashville, TN), Oak Ridge National laboratory (Oak Ridge, TN), and the University of Tennessee (Knoxville, TN) have come up with a laser-based phenomenon that could do just that, and are scratching their heads as to why it works.

Hydrogen (H) is sometimes added to a silicon (Si) chip in manufacture as a temporary oxidization barrier, and is normally removed by heating the chip to almost 900°C-hot enough to cause defects that lower chip yields. The scientists avoid this by photodesorbing H from Si at room temperature in ultrahigh vacuum with tunable IR laser light from the pulsed free-electron laser at Vanderbilt. They discovered that H desorbed best at a wavelength of 4.8 µm, corresponding to the 0.26 eV energy of the Si-H bond’s vibrational stretch mode. But a detailed understanding of the physical mechanism behind the process is yet to be found. Contact Philip Cohen at [email protected].