Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 11: Neue Materialien

HL 11.4: Talk

Monday, March 8, 2004, 16:00–16:15, H14

Self-Organization of Nanocluster δ-Layers at Ion-Beam-Mixed Si-SiO₂ Interfaces — •Lars Röntzsch, Karl-Heinz Heinig, and Bernd Schmidt — FZ-Rossendorf, Bautzner Landstraße 128, 01328 Dresden

The Multidot Nano-flash Memory suggested by Tiwari [APL69(1996)1232] is a promising candidate for succeeding the Floating Gate Flash Memory.

Its most challenging configurational feature is a layer of Si nanoclusters (NCs) within the oxide of a MOS-like structure.

Here, we present experimental evidence that the concept predicting the self-organization of a Si NCs δ-layer at an ion irradiated Si-SiO₂ interface is valid (cf. Heinig [APA77(2003)17]).

Unconventionally, a 15nm thin SiO₂ layer, which is enclosed by a 50nm poly-Si capping layer and the Si substrate, is irradiated with Si⁺ ions. Ion impact drives the system to a state far from thermodynamic equilibrium, i.e. the local composition of the target is modified to a degree unattainable in common processes. A region of SiO_x (x<2; x is a function of depth) is formed which is not stable.

During annealing, the system relaxes towards equilibrium, i.e. phase separation (via spinodal decomposition and nucleation) sets in. Within a certain time window of annealing, the structure of the system matches with a structure similar to the Multidot Memory device.

The experimental handicap that tiny Si NCs (d<3nm) which are embedded in SiO₂ are not visible in common XTEM is resolved by a novel method which applies Ge as contrast enhancing element in TEM studies of tiny Si NCs.