Silicon substrate damage caused by HBr/O 2 plasma exposure was investigated by spectroscopic ellipsometry (SE), high-resolution Rutherford backscattering spectroscopy, and transmission electron microscopy. The damage caused by H 2 , Ar, and O 2 plasma exposure was also compared to clarify the ion-species dependence. Although the damage basically consists of a surface oxidized layer and underlying dislocated Si, the damage structure strongly depends on the incident ion species, ion energy, and oxidation during air and plasma exposure. In the case of HBr/O 2 plasma exposure, hydrogen generated the deep damaged layer ($10 nm), whereas ion-enhanced diffusion of oxygen, supplied simultaneously by the plasma, caused the thick surface oxidation. In-line monitoring of damage thicknesses by SE, developed with an optimized optical model, showed that the SE can be used to precisely monitor damage thicknesses in mass production. Capacitance-voltage (C-V) characteristics of a damaged layer were studied before and after diluted-HF (DHF) treatment. Results showed that a positive charge is generated at the surface oxide-dislocated Si interface and/or in the bulk oxide after plasma exposure. After DHF treatment, most of the positive charges were removed, while the thickness of the "Si recess" was increased by removing the thick surface oxidized layer. As both the Si recess and remaining dislocated Si, including positive charges, cause the degradation of electrical performance, precise monitoring of the surface structure and understanding its effect on device performance is indispensable for creating advanced devices. V

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The wavelength dependence of SiN x :H/Si interface defect generation caused by vacuum ultraviolet (VUV)/UV radiation from plasma etching processes was investigated. VUV radiation (λ< 200 nm) had almost no impact on the generation of defects at the SiN x :H/Si interface, since all the radiation in this wavelength range was absorbed in the upper SiN x :H film. However, UV radiation (200 < λ< 400 nm) was able to reach the underlying SiN x :H/Si interface and damage the interface. Direct UV radiation reaching the SiN x :H/Si interface dissociated the chemical bonds at the interface and generated interface-trapped charges. The estimated total energy of absorbed photons (E total; 200 < λ< 400 nm) at the interface layer seems to be proportional to the interface-trapped charge density (D it) measured by capacitance–voltage measurement. However, the mechanism underlying the relationship between E total and D it is not yet clear. Visible radiation (λ> 400 nm) had no influence on damage generation on the SiN x :H/Si structure, since the visible radiation was transmitted through upper SiN x :H film and underlying interface layer. The results revealed that UV radiation transmitted through the upper dielectrics can cause the electrical characteristics of underlying metal–oxide–semiconductor (MOS) devices to fluctuate.

Photon-enhanced etching of SiN x :H films caused by the interaction between vacuum ultraviolet (VUV)/ultraviolet (UV) radiation and radicals in the fluorocarbon plasma was investigated by a technique with a novel sample setup of the pallet for plasma evaluation. The simultaneous injection of UV radiation and radicals causes a dramatic etch rate enhancement of SiN x :H films. Only UV radiation causes the film shrinkage of SiN x :H films owing to hydrogen desorption from the film. Capacitance–voltage characteristics of SiN x :H/Si substrates were studied before and after UV radiation. The interface trap density increased monotonically upon irradiating the UV photons with a wavelength of 248 nm. The estimated effective interface trap generation probability is 4.74 ×10-7 eV-1·photon-1. Therefore, the monitoring of the VUV/UV spectra during plasma processing and the understanding of its impact on the surface reaction, film damage and electrical performance of underlying devices are indispensable to fabricate advanced devices.

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