From: hackbard Date: Wed, 20 Apr 2011 15:04:55 +0000 (+0200) Subject: finished ibs part, go on with c in c-si + precipitation model controversy X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=commitdiff_plain;h=9a540409168f421fb8eee3861a1fe8d6e3a28b38 finished ibs part, go on with c in c-si + precipitation model controversy --- diff --git a/posic/thesis/sic.tex b/posic/thesis/sic.tex index 256e7db..9926ccd 100644 --- a/posic/thesis/sic.tex +++ b/posic/thesis/sic.tex @@ -262,24 +262,43 @@ Therefore, the dose must not exceed the stoichiometry dose, i.e. the dose corres Otherwise clusters of C are formed, which cannot be dissolved during post-implantation annealing at moderate temperatures below the Si melting point \cite{lindner96,calcagno96}. Annealing should be performed for \unit[5-10]{h} at \unit[1250]{$^{\circ}$C} to enable the redistribution from the as-implanted Gaussian into a box-like C depth profile \cite{lindner95}. The implantation temperature constitutes the most critical parameter, which is responsible for the structure after implantation and, thus, the starting point for subsequent annealing steps. - - -\cite{lindner98} sharp interface and good crystallinity - -improved two-temperature implantation \cite{lindner99}. - -By understanding these basic processes -... lindner limit in dose -> 1250 -... two temp implantation ... sharp interface -By understanding some basic processes (32-36), \ac{IBS} nowadays has become a promising method to form thin SiC layers of high quality exclusively of the 3C polytype embedded in and epitactically aligned to the Si host featuring a sharp interface \cite{lindner99,lindner01,lindner02}. +Implantations at \unit[400]{$^{\circ}$C} resulted in buried layers of SiC subdivided into a polycrystalline upper and an epitaxial lower part. +This corresponds to the region of randomly oriented SiC crystallites and epitaxially aligned precipitates surrounded by thin amorphous layers without crystalline SiC inclusions in the as-implanted state. +However, an abrupt interface to the Si host is observed after annealing. +As expected, single-crystalline layers were achieved for an increased temperature of \unit[600]{$^{\circ}$C}. +However, these layers show an extremely poor interface to the Si top layer governed by a high density of SiC precipitates, which are not affected in the C redistribution during annealing and, thus, responsible for the rough interface. +Hence, to obtain sharp interfaces and single-crystalline SiC layers temperatures between \unit[400]{$^{\circ}$C} and \unit[600]{$^{\circ}$C} have to be used. +Indeed, reasonable results were obtained at \unit[500]{$^{\circ}$C} \cite{lindner98} and even better interfaces were observed for \unit[450]{$^{\circ}$C} \cite{lindner99_2}. +To further improve the interface quality and crystallinity a two-temperature implantation technique was developed \cite{lindner99}. +To form a narrow, box-like density profile of oriented SiC nanocrystals \unit[93]{\%} of the total dose of \unit[$8.5\cdot 10^{17}$]{cm$^{-2}$} is implanted at \unit[500]{$^{\circ}$C}. +The remaining dose is implanted at \unit[250]{$^{\circ}$C}, which leads to the formation of amorphous zones above and below the SiC precipitate layer and the desctruction of SiC nanocrystals within these zones. +After annealing for \unit[10]{h} at \unit[1250]{$^{\circ}$C} a homogeneous, stoichiometric SiC layer with sharp interfaces is formed. + +To summarize, by understanding some basic processes, \ac{IBS} nowadays has become a promising method to form thin SiC layers of high quality exclusively of the 3C polytype embedded in and epitaxially aligned to the Si host featuring a sharp interface. +Due to the high areal homogeneity achieved in \ac{IBS}, the size of the layers is only limited by the width of the beam-scanning equipment used in the implantation system as opposed to deposition techniques, which have to deal with severe wafer bending. +This enables the synthesis of large area SiC films. \section{Substoichiometric concentrations of carbon in crystalline silicon} -diffusion mechanism, lattice distortion, hmm ... extra section needed? +The C solid solubility in bulk Si is quite low +% carbon as an impurity / solubility / lattice distortion / diffusion +% agglomeration phenomena +% suppression of transient enhanced diffusion of dopant species +% strained silicon / heterostructures +% -> skorupa 3.2: c sub vs sic prec +% -> my own links: strane etc ... +% -> skorupa 3.5: heterostructures + +% hmm ... extra section needed? \section{Assumed cubic silicon carbide conversion mechanisms} \label{section:assumed_prec} +Although much progress has been made in 3C-SiC thin film growth in the above-mentioned growth methods during the last decades, there is still potential +.. compatible to the established and highly developed technology based on silicon. + +Although tremendous progress has been achieved in the above-mentioned growth methods during the last decades, available wafer dimensions and crystal qualities are not yet statisfactory. + ... \cite{lindner99_2} ... on surface ... md contraction along 110 ... kitabatake ... and ref in lindner ... rheed from si to sic ... @@ -292,3 +311,4 @@ nejim however ... also indictaed by other direct synthesis experiments like martin90 and conclusions of reeson8X ... eichhornXX, koegler, lindner ... +