Al-O interactions in ion-implanted crystalline silicon

Abstract

The formation and dissolution of Si-O-Al precipitates have been investigated in Czochralski silicon wafers implanted with 6 MeV Al ions and thermally processed. The data have been compared to the O precipitation in samples implanted with 6 MeV Si or P ions. The amount of precipitated O atoms is about one order of magnitude higher for Al than for Si or P implanted samples. Moreover, a strong gettering of the Al atoms by the silicon dioxide precipitates has been observed. The precipitate evolution has been studied for different annealing times and temperatures. The oxygen precipitation has been simulated by the classical theory of nucleation and growth, with the introduction of new factors that take into account the implant damage distribution, the agglomeration of point defects during the initial stages of the annealing and the oxygen outdiffusion from the sample surface.

Thermal Oxidation of High Dose Aluminum Implanted Silicon

“…3 The Al solid solubility in Si is quite low (1 ϫ 10 19 cm Ϫ3 at 900ЊC 4 ); however, even at a concentration below solid solubility, Al x O y precipitates are formed due to the high reactivity of Al with the oxygen present in the Czochralski grown wafers (oxygen content 10 18 cm Ϫ3 ). 5 No precipitation occurs if implants are performed into epitaxially grown Si, where the oxygen content is less than 1 ϫ 10 16 cm Ϫ3 , and the Al concentration does not exceed the solid solubility limit. However, the oxygen concentration can be high also in epi layers after an oxidation process due to the oxygen drive-in and diffusion from the surface to the bulk.…”

Oxidation induced precipitation in Al implanted epitaxial silicon

“…It has been demonstrated in previous works that precipitation occurs where damage, aluminum, and oxygen are simultaneously present. [2][3][4] To understand the phenomenon taking place during oxidation, the injected oxygen distribution has been calculated using the model described in Ref. 11.…”

“…The main problems associated with the use of Al implants, however, are the outdiffusion from the sample during the driving process 1 and its reactivity with oxygen atoms. 2,3 The latter phenomenon causes Al precipitation in proximity to the implant-induced defects that act as nucleation centers for the formation of Al x O y clusters. This occurs in Czochralski-grown substrates where the bulk oxygen concentration is about 8ϫ10 17 atom/cm 3 .…”

“…Indeed, the precipitation is absent in epitaxial layers where the oxygen content is less than 1ϫ10 16 atom/cm 3 , or if the presence of defects is avoided as, for instance, by Al predeposition. 2,4 Otherwise, even for Al implants in epitaxial layers, precipitation might occur if thermal oxidation processes are employed for the device fabrication. 5 In fact, during oxidation, oxygen is introduced at a concentration about one order of magnitude higher than the equilibrium solid solubility characteristic of samples well annealed in an inert ambient.…”

Two‐Dimensional Aluminum Diffusion in Silicon: Experimental Results and Simulations

“…The formation of these precipitates and their evolution as a function of the diffusion time and temperature has been previously investigated. 3 It was found that the amounts of A1 and O into the precipitates follow the same trend revealing a strong interaction between the SiO2 precipitates and the implanted aluminum. This phenomenon is mainly observed on Czochralski-grown silicon wafers where the oxygen bulk concentration is about 8 X 10~7/cm 3.…”