Ionized physical-vapor deposition using a hollow-cathode magnetron source for advanced metallization

The hollow-cathode magnetron (HCM) source is a new and promising technology for metal deposition that maintains the simplicity of the physical-vapor deposition technology and combines it with a very high-density diffused plasma (>10 12 #/ cm 3 ) for efficient ionization of sputtered metals. The HCM employs a magnetron discharge confined in an inverted cup-shaped target. As such, it does not require any additional rf or microwave sources for generation of metal ions. In this article, the HCM theory of operation will be reviewed and results will be presented for the application of this source for deposition of Ti(N), Ta(N), and Cu films. In addition, the effects of rf bias on step coverage and film properties will be discussed. In particular, enhanced bottom coverage (20% for Cu, 40% for Ta, and 30% for Ti) in narrow, high-aspect-ratio vias (0.25 μm, 5:1 AR) was obtained without the application of rf bias to the wafer. Both TiN and TaN films had the same step coverage as Ti and Ta films, respectively. Rf bias was utilized to further increase the bottom coverage and the sidewall coverage of the films, thus extending the technology to higher aspect ratios. In addition, rf bias was used to modify film properties such as grain size, grain orientation, and film texture.