Slot-excited Antenna Research Articles

Etching characteristics of hydrogenated amorphous silicon and poly crystalline silicon by hydrogen hyperthermal neutral beam

A hydrogen hyperthermal neutral beam (HNB) generated by an inclined slot-excited antenna electron cyclotron resonance plasma source has been used to etch hydrogenated amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) films. In this work, we present selective etching of a-Si:H with respect to poly-Si by hydrogen plasma and hydrogen HNB under various substrate temperatures, gas pressures, and bias voltages of the neutralizer. We have observed that the etch rate of a-Si:H is considerably higher than that of poly-Si. The etch rate is largely dependent upon the substrate temperature. In this experiment, the optimal substrate temperature for improving the etch rate is approximately at 150°C. The root mean square surface roughness of the etched material reaches a maximum at 150°C and decreases rapidly. The etch rate of poly-Si is not sensitive to changes in the experimental condition, such as the substrate temperatures and gas pressures. However, as the hydrogen HNB energy is increased, the etch rate of poly-Si also increases gradually. The hydrogen HNB energy contributes in improving the etch rate of a-Si:H and poly-Si films.

Waveguide slot-excited long racetrack electron cyclotron resonance plasma source for roll-to-roll (scanning) processing

We present a SLot-excited ANtenna (SLAN) long racetrack ECR plasma source that is utilized for roll-to-roll plasma processing such as thin film encapsulation of large-area OLED (organic light emitting diode) panel or modification of fabric surfaces. This source is designed to be long, and to operate under high density uniform plasma with sub-milli-torr pressures. The above features are accomplished by a slot-excited long racetrack resonator with a toroidal geometry of magnetic field ECR configuration, and reinforced microwave electric distributions along the central region of plasma chamber. Also, a new feature has been added to the source. This is to employ a tail plunger, which allows the microwave electric field and the uniformity of the plasma profile to be easily adjustable. We have successfully generated Ar plasmas operating with the microwave power of 0.5-3 kW in the pressure range of 0.2-10 mTorr. The plasma is uniform (<10%) in the direction of the straight track and has a Gaussian profile in the roll-to-roll (scanning) direction. In addition, it is shown that the tail plunger could adjust the plasma profile in order to obtain plasma uniformity. Furthermore, based on the results, we suggest a newly designed up-scaled racetrack-SLAN source.

Analysis of the crystalline characteristics of nc-Si:H thin film using a hyperthermal neutral beam generated by an inclined slot-excited antenna

The deposition of hydrogenated nano-crystal silicon (nc-Si:H) thin film for manufacturing quantum dot solar cells, which has received attention due to the use of this film third-generation solar cells, is studied here. A hyperthermal neutral beam (HNB) generated by an inclined slot-excited antenna plasma source is used to reduce damage to the silicon thin film and deposition of the crystalline thin film is carried out on a substrate at a low temperature (<200°C). The size and the crystalline fraction of the nc-Si:H of the deposited thin film were analyzed by scanning transmission electron microscopy and a Raman microscope. As a result, silicon crystals 1–10nm in size were observed in the amorphous silicon matrix. According to previous studies, the size and the crystalline fraction of nc-Si:H in deposited thin films increase as the hydrogen flow rate is increased. However, the increment of hydrogen flow rate decreases the deposition rate rapidly. The size and the crystalline fraction of nc-Si:H are adjustable by varying the substrate temperature and HNB energy without a change of the hydrogen flow rate. There are optimum conditions between the HNB energy and the substrate temperature for an appropriate amount of nc-Si:H in silicon thin film.

Inclined slot-excited annular electron cyclotron resonance plasma source for hyperthermal neutral beam generation

An inclined slot-excited antenna (ISLAN) electron cyclotron resonance (ECR) plasma source is newly designed and constructed for higher flux hyperthermal neutral beam (HNB) generation. The developed ISLAN source is modified from vertical slot-excited antenna (VSLAN) source in two aspects: one is the use of inclined slots instead of vertical slots, and the other is a cusp magnetic field configuration rather than a toroidal configuration. Such modifications allow us to have more uniform arrangement of slots and magnets, then enabling plasma generation more uniform and thinner. Moreover, ECR plasma allows higher ionization rate, enabling plasma density higher even in submillitorr pressures, therefore decreasing the collision rate and∕or the reionization rate of the reflected atoms while passing through the plasma, and eventually getting higher flux of HNBs. In this paper, we report the design features and the plasma characteristics of the ISLAN source by doing plasma measurements and electromagnetic simulations. It was found that ISLAN source can be a high potential source for larger flux HNB generation; the source was found to give higher plasma densities and better uniformities than inductively coupled plasma source, particularly in low pressure ranges. Also, it is important that using ISLAN gives easier matching and better stability, i.e., ISLAN shows similar field patterns and good plasma symmetries irrespective of the variations of the mean diameter of the ring resonator and∕or the presence of a limiter or a reflector, and the operating pressures.