We study the effects of annealing temperature on oxide charge trapping near the SiO2/Si interface using time-dependent second harmonic generation (TD-SHG), which is sensitive to charge separation near the interface. The TD-SHG signals are measured in plasma enhanced tetraethyl orthosilicate (PE TEOS) and high density plasma (HDP) oxide films deposited on silicon, respectively, which are typically used as intermetal dielectric (IMD) layers in 3D NAND. After annealing at temperatures ranging from 550 °C to 850 °C, the initial slopes of the TD-SHG signals at t=0, related to the charge trap density, decrease with increasing annealing temperature for PE TEOS, while the signals from HDP oxides show relatively flat curves independent of temperature even in the as-deposited state due to the reduced charge traps. The direction of the interfacial electric field resulting from the charge separation can be interpreted from the sign of the measured slopes. In PE-TEOS oxides annealed above 800 °C, the slope changes to the opposite sign, indicating the dominance of negative charges rather than positive charges. The observed TD-SHG results support previous suggestions that the electron trapping occurs in the carbon-related center of TEOS and appears to be dominant after high temperature annealing.
In this paper, we suggested an alignment mark measurement system for die-to-wafer bonder. The system consisted of a vision system to measure the positions of alignment marks on die and wafer opposite to each other, and a height measurement system to detect the heights of the die and wafer to the vision system. Besides them, a tilt measurement system was also attached to check the parallelism between the die and wafer for exact measurement and bonding. For high precision measurement, the vision system used a special prism structure which minimized the distance between the die and wafer and measured alignment marks on both sides simultaneously. A focus tunable lens was also applied to control a focus position without changing the height of the system. We have designed and built the optical system in a compact size and presented some preliminary results here.
We demonstrate the broadband visible luminescence from bulk crystalline silicon and silicon nanoparticles sized 100- 30 nm under near-infrared excitation. We show that the luminescence spectrum has two distinct peaks. The first being centered at 550 nm while the second appears close to the wavelength of the second harmonic of the excitation light. The appearance of the second peak is a signature of the highly athermal electron distribution never observed previously. The luminescence intensity and spectral shape strongly depend on the doping type and concentration. Despite being nonresonant, silicon nanoparticles enhance luminescence intensity when placed atop the silicon wafer. The observed phenomenon can be used for wafer inspection and defect detection, as well as for the creation of novel nanosources of light.
We present a novel optical device which interchanges two orthogonal directions in the cross-section of a beam. The optical prism is composed of six flat faces and has particular edge angles. The beam passing through the component is totally reflected at right angles inside the prism and flipped diagonally at the exit with respect to the entrance. When a line beam is incident to the device, the beam is segmented step by step at the first side face and combined on the other side. The overall shape of the line beam is maintained at the exit, but the segments of the line beam are flipped. The narrow axis of the line beam at the exit has the divergence angle corresponding to the long axis at the entrance. The component is also useful to focus beams from linear laser diode array with asymmetric divergence angles. Compared to the other beam transformation systems, the suggested device has advantages of easy fabrication, coating-free and no energy loss on reflective surfaces.
Detection of a single nanoparticle on a bare silicon wafer has been a challenge in the semiconductor industry for decades. Currently, the most successful and widely used technique is dark-field microscopy. However, it is not capable of detecting single sub-10 nm particles owing to a low signal-to-noise ratio (SNR). As a new approach, we suggest using the second harmonic generation (SHG) to detect a single nanoparticle. The second harmonic generation in centrosymmetric materials, like silicon, is forbidden except for a thin and additionally increase local field factors, allowing for their persistent detection. Choosing the proper surface and increasing SNR. We demonstrate the feasibility of the nonlinear dark-field microscopy concept by detecting an isolated 80-nm silicon nanoparticle on the silicon wafer.
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