Ion-assisted sputter deposition and structural characterization of cubic boron nitride
We have grown cubic boron nitride (c-BN) films on silicon (100) substrates by rf magnetron sputter deposition in the presence of an electron cyclotron resonance source (ECR) nitrogen plasma. By applying a negative dc potential to the substrate, we are able to accelerate the nitrogen ions from the EC...
Saved in:
| Main Author: | |
|---|---|
| Format: | Electronic |
| Language: | Undetermined |
| Published: |
1994.
|
| Subjects: | |
| Online Access: | Access restricted to UM users and campus guests: Access to the ProQuest dissertations & theses online version restricted; authentication may be required: |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | We have grown cubic boron nitride (c-BN) films on silicon (100) substrates by rf magnetron sputter deposition in the presence of an electron cyclotron resonance source (ECR) nitrogen plasma. By applying a negative dc potential to the substrate, we are able to accelerate the nitrogen ions from the ECR providing more energy to the growth surface. We have investigated the growth conditions, particularly the effect of substrate bias and ion energies on growth. The structure of the films has been analyzed by reflective high energy electron diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and high resolution electron microscopy. We find evidence that the formation of c-BN requires irradiation of the growth surface with energetic species on the order of 100 eV, much lower than previously reported. For our deposition system, this minimum kinetic energy manifests itself as a threshold in the substrate bias potential. The structure of the films changed from entirely hexagonal (h-BN) to predominantly cubic over a very small range in the substrate bias voltage ($\pm$5 V). Moreover, the crystal structure is optimized in a small range beyond the threshold with bias voltages just a few volts higher causing a significant decrease in crystal quality. Our finding is, to the best of our knowledge, the first evidence of a sharp, low energy threshold for c-BN formation. High resolution electron microscopy studies show that the films have a layered structure with a thin (40 A) amorphous layer next to the silicon, followed by a thin (300 A) layer of textured h-BN aligned with the c-axis parallel to the substrate surface. Single-phase, polycrystalline c-BN comprises the rest of the film. The h-BN is confined to the interfacial region and once c-BN forms it is the preferred phase in the deposition. We discuss the important role of energetic ions in the formation of c-BN. In particular, recent molecular dynamics simulations provide quantitative evidence for bonding kinetics at impulse energies similar to those we have observed experimentally. |
|---|---|
| Item Description: | Digitized from microform version. |
| Bibliography: | Includes bibliographical references. |