Study On Laser Of Different Wavelengths Interaction With Silicon-on-Insulator Material

Silicon-on-Insulator (SOI) Technology, which has a broad prospect of applications, has been gradually replacing the bulk silicon technology. Laser induced damage threshold is a property index of quite importance when evaluating the application ability of SOI materials in electronic devices. However, study on laser induced damage and ablation mechanism on SOI material and devices are comparatively less. Laser damage threshold on and ablation mechanism on SOI material are investigated by pulsed (-10nanoseconds) laser radiation of different wavelengths (1064nm,532nm,355nm) in this paper. The damage threshold and temperature distribution of SOI after laser irradiation is obtained by means of simulations and experiments.The effect of different producing process of SOI on property is analysed. Because of the small bandgap of surface crystalline silicon layer, it is easy to couple with laser of wavelengths from0.3μm to0.1μm by intrinsic absorption, which has a high efficiency. The low thermal conductivity of the buried SiO2layer leads to the consequence that heat generated in SOI devices is hard to go out via the substrate layer, resulting in self-heating effect. It should be noticed when researching and applying.The interaction mechanism between laser and SOI materials is investigated. The interaction of light with semiconductor is achieved by the way of external electric field driving electrons in the semiconductors to oscillate. The eigenfrequencies of electronics are determined by the energy band structure of the material. When laser frequency getting close to the eigenfrequencies, coupling efficiency is higher. In general, absorption coefficient of the sufface c-silicon layer increases as the wavelength decreases, but there will be absorption peaks at some wavelengths. This feature reflects the inherent physical properties of c-silicon. When radiation time of laser from near-UV to infrared on c-silicon is longer than the relaxation time within the photons, electrons and phonons subsystems, laser energy turns into thermal energy of the crystal lattice, and the heating depth is dependent on absorption coefficient, thermal diffusion lenth and carrier lifetime. Hence, laser with wavelength from355nm to1064nm irradiating on SOI material can be described by the thermal conduction equation.The temperature distribution after radiation and damage threshold of SOI irradiated by laser wavelengths of355nm,532nm and1064nm are simulated, repectively. In the situation of1064nm and532nm laser damage, the complete structure of SOI is considered, while in the355nm situation, only surface Si layer is analyzed. The results show that (a)1064,532,355nm laser damage threshold of SOI material are4.7J/cm2,0.82J/cm2,0.25J/cm2respectively,(b) the temperature distributions after interaction with diffetent wavelengths give an expression that the self-heating effect is caused by the buried oxide layer, acting as thermal barrier, in the SOI devices.The1-on-1damage measurement is used to study the laser damage threshold of SOI material of three laser wavelengths:1064nm,532nm,355nm. As wavelengths decreases, thermal effect on the surface is recedes, and the damage threshold decreases. The laser damage threshod of SOI are1.68J/cm2,0.45J/cm2,0.28J/cm2for the wavelengths of1064nm,532nm,355nm respectively when taking the super-Gaussian distribution of laser spot and environment of the experimentsinto calculation.