METHOD FOR HIGH EFFICIENCY GETTERING CONTAMINANTS AND DEFECTS IN A SEMICONDUCTOR BODY

摘要

A semiconductor wafer into which devices such as an integrated circuit is to be formed is gettered by regions in the wafer activated by a laser beam. The laser beam is directed onto the surface of the wafer opposite to that where the devices are to be formed. The power input to the laser is controlled such that the surface temperature of the region of the semiconductor wafer where the laser beam is applied first reaches the melting point of the material, such as silicon, and the melting commences. Then the temperature in the melt rises above the melting temperature, but stays below the boiling temperature of the material of the wafer. A superheated melt is formed. The result is that the solid-liquid interface moves deep into the material. The position of the melt is directly under the laser beam. The solidified material is positioned behind the beam as the beam scans the wafer. A depression is formed under the beam while the material rises behind the laser beam. This depression effect of the laser beam causes the beam to penetrate relatively deeply into the material. The superheated melt of this type has been found to be useful in the activation of internal gettering centers as opposed to crystal damage by a higher powered laser beam. These internal gettering centers, which may be oxygen complexes or the like, then act as gettering sites for unwanted impurities during subsequent heat treatment of the semiconductor wafer.