Laser removal of impurity particles from silicon wafer surface

number: 
1808
إنجليزية
Degree: 
Author: 
Hiba Khudhair Abbas Al-Jumaili
Supervisor: 
Hassan W. Hilou
year: 
2007
Abstract:

In this work, the laser cleaning method is used and studied. A thin aluminum layer of lum thickness has been evaporated on a silicon wafer (p-type) surface. This sample has been treated using a solid-state, Nd: YAG pulsed laser with a wavelength of 1.064 urn and 20 ns pulse duration. Laser beam energy varied from 14.5 mJ to 100 mJ in four steps. Samples are tested using optical microscope and then digital images are taken to each sample using digital camera connected to a computer with USB interface. These images are analyzed using a MATLAB 7.0 and image processing package. An analysis process is done on these images to clarify the removal process step by step. The results obtained in this work showed that the removed thickness of the aluminum particles is increased with the increase of laser beam energy. The suitable beam energy to remove a lum of aluminum thickness is (100 mJ) with (20) pulses. A He: Ne laser system has also been used to determine the cleaning efficiency (TJ) by the measurement of the laser beam scattered from the silicon wafer surface. It is found that cleaning efficiency (n) for the energy of: 14.5 mJ, 22.5 mJ, 50.2 mJ and 100 mJ are: 18.67 %, 31.323 %, 56.63 % and 80.1 % respectively.