Electrical properties of contact etched p-Si: A comparison between magnetically enhanced and conventional reactive ion etching

Abstract

We report the results of a comparative study of the damage induced in boron-doped Si by contact etching. The two approaches compared are conventional reactive ion etching and magnetically enhanced reactive ion etching (MERIE). The two structure-chemistry combinations used are SiO2/Si with CHF3/O2 plasmas, and bare Si wafers with CHF3/Ar plasmas. The damage examined in the Si substrates of both structures is that of electronic states in the band gap, the permeation into Si of hydrogen, and the deactivation of boron acceptors. These types of damage are explored by means of deep level transient spectroscopy and capacitance-voltage measurements on Ti/Si Schottky diodes fabricated on the etched substrate surfaces. The gap states induced by these contact etches are ascribed to interstitial-atom-related defects which are proposed to be formed as a result of interactions involving self interstitials. During etching these defects are observed to be both generated by the etching process itself as well as electrically passivated by permeating hydrogen. The hydrogen permeation of the substrate, monitored via acceptor deactivation, is seen to be enhanced for MERIE with increasing magnetic field intensities.

Estimation of defect generation probability in thin Si surface damaged layer during plasma processing

“…In the structural analysis, in addition to spectroscopic ellipsometry used in production lines, reflected high-energy diffraction [5,9], X-ray photoelectron spectroscopy [10], and photoreflectance spectroscopy [11][12][13] have been employed. In the electrical measurements, the current-voltage measurement with Schottky-contact test structures [7,9,11], sheet resistance measurement [8] and deep-level transient spectroscopy [14] have been performed to investigate the defects in devices. However, compared to extensive studies of the charging damage [3], the defect generation processes have not been investigated so far in terms of a quantitative parameter such as carrier trap site density closely related to the device performances.…”

RIE‐induced carrier lifetime degradation

“…Agostinelli studied the benefit of dry etching for integration to obtain improved performance and lower environmental impact [11,12]. However, RIE generates defects in the near-surface region of the semiconductor [13][14][15], thus degrading the electrical performance of solar cells and other devices [16][17][18][19]. Deenapanray characterised the reaction mechanism of RIE etching of silicon, SiO 2 and SiN x against varied etch parameters [20,21], and also studied lifetime degradation and defect characterisation in RIE-processed silicon samples [22].…”

Reactive ion etching of dielectrics and silicon for photovoltaic applications

“…11,12 The creation of defects in the near-surface region of plasma processed semiconductors is well documented. 3,[10][11][12][13][14] In the presence of electrically active defects that may act as recombination centers, the electrical properties of the solar cells usually degrade. 10,15 Defect creation during plasma processing of semiconductors has been an obstacle for the adoption of dry processing in the fabrication of solar cells, and, as such, is the main driving force behind the design and implementation of near-damage-free plasma processing for photovoltaic applications.…”