| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | M. Fukasawa, Sony Corporation, Japan |
| Authors: | M. Fukasawa, Sony Corporation, Japan Y. Miyawaki, Nagoya University, Japan Y. Kondo, Nagoya University, Japan K. Takeda, Nagoya University, Japan H. Kondo, Nagoya University, Japan K. Ishikawa, Nagoya University, Japan M. Sekine, Nagoya University, Japan H. Matsugai, Sony Corporation, Japan T. Honda, Sony Corporation, Japan M. Minami, Sony Corporation, Japan F. Uesawa, Sony Corporation, Japan M. Hori, Nagoya University, Japan T. Tatsumi, Sony Corporation, Japan |
| Correspondent: | Click to Email |
Incident species from plasma needs to be strictly controlled to fabricate advanced devices. We found that simultaneous injection of VUV/UV radiation and radicals caused the marked etch rate enhancement of SiNx:H films [1]. This indicates that not only ions, but also VUV/UV radiation affects the surface reaction of radicals with SiNx:H. In this study, we investigated the effect of transmitted VUV/UV radiation on underlying interface traps of SiNx:H/Si substrate by using the pallet for plasma evaluation (PAPE) [2].
A dual frequency (60/2 MHz) CCP reactor was used. SiNx:H films were deposited on Si substrates by PECVD and those were exposed to CF4/O2 plasma. The thicknesses of SiNx:H films were 200 nm. To investigate the effect of radiation, MgF2 (> 115 nm), quartz (> 170 nm), and borosilicate crown glass BK7 (> 300 nm) windows were put directly on the SiNx:H film. The capacitance-voltage (C–V) characteristics of SiNx:H on Si substrate were analyzed to study the interface-trap density (Dit).
The penetration depths of photons strongly depend on the wavelength of the VUV/UV radiation and the absorption coefficient of materials. The wavelengths of photons were classified into three major ranges by their interaction with the material:
1) Photons are absorbed in the material and damage the film and/or enhance the surface reaction [1].
2) Photons are transmitted through the material and absorbed in the underlying interfaces, resulting in the increase in Dit.
3) Photons are transmitted through both the material and interface, and there is no impact on the damage generation.
The Dit increase is the most serious issue for advanced device fabrication since the Dit directly degrades electrical performance. Thus, the damage of SiNx:H/Si substrate interface was investigated by C–V measurement. The Dit of SiNx:H/Si substrate was unaffected by the VUV radiation (< 170 nm) since all the high-energy photons were absorbed in the SiNx:H film (case 1). When the photons in the UV region (> 170 nm) were irradiated, the Dit increased and a negative charge was generated in the interface (case 2). This indicates that the VUV/UV radiation transmitting through the upper dielectrics causes the electrical characteristics of underlying devices to fluctuate. The UV radiation (> 300 nm) had almost no effect on the increase in Dit (case 3) due to the lack of absorption in both the material and interface.
Thus, the wavelength dependence of increases in Dit needs to be investigated for possible interfaces in advanced devices.
[1] M. Fukasawa et al., Jpn. J. Appl. Phys., 51 (2012) 026201.
[2] S. Uchida et al., J. Appl. Phys., 103 (2008) 073303.