Silicon Carbide Wafer Machining by Using a Single Filament Plasma at Atmospheric Pressure

SiC wafers were etched using a filament plasma of He:NF3:O2 (helium:nitrogen trifluoride:oxygen) mixed gas at atmospheric pressure. When 0.5–2 sccm of NF3 was mixed to 2 slm of He filament plasma, the etch depth and etch rate increased, but there was little change in the etch width as the NF3 mixing amount increased. The increment of the NF3 mixing also suppressed the surface roughening of plasma etching. The addition of O2 to the He-NF3 filament plasma slightly increased the SiC wafer etch rate. When the NF3 mixing amount was 2 sccm, the roughness of the etched surface increased sharply by O2 addition. On the contrary, the NF3 mixing amount was 1 sccm; the addition of O2 reduced the roughness more than that of the pristine. The roughness of the pristine SiC wafer specimens is in the range of Ra 0.7–0.8 nm. After 30 min of etching on a 6 mm by 6 mm square area, the roughness of the etched surface reduced to Ra 0.587 nm, while the etch rate was 2.74 μm/h with a He:NF3:O2 of 2:1:3 (slm:sccm:sccm) filament plasma and 3 mm/s speed of raster scan etch of the optimized roughening suppression etching recipe.

Plasma Channel Extension by Femtosecond Laser Filamentation with a Circular Aperture Quartz Plate

We propose a new approach of extending the laser filament plasma channel. By adding a circular aperture quartz plate before the focusing lens, the extension of the plasma channel is doubled. The effects of different diameters, thicknesses of the circular aperture quartz plate and different pulse energies on the length of the plasma channel were investigated. The experimental results show that the thickness of the quartz plate and the depth of the hole have little effects on the plasma channel of the filament, and the diameter of the hole in the center of the quartz plate has a significant effect on the length of the optical filament. The moving-focus model is used to explain the extension of the optical filament.

LEDs for Solid-State Lighting

Solid-state lighting technology is rapidly gaining acceptance in lighting industry street lighting, traffic lighting, decorative lighting, projection displays, display backlighting, automotive lighting, and so on. Differing from conventional light sources that use tungsten filament, plasma, or gases to generate light, solid-state lighting is based on organic or inorganic light emitting diodes (LEDs), and has the potential to generate light with almost 100 % efficiency. LED luminaires have a long lifetime and are environmentally friendly with no toxic mercury contained. However, the success of these luminaires depends on system design, which comprises an understanding of several factors such as performance and control. In this chapter, we shall touch upon some technological advancements in the field of solid-state lighting technologies and challenges that limit their market penetration for consumer lighting.