Cu In Silicon Research Articles

Phosphorus gettering of precipitated Cu in single crystalline silicon based on rapid thermal process

In this paper, we have investigated the effect of phosphorus diffusion gettering on the precipitated Cu in silicon via rapid thermal process (RTP). It is found that, for dot-like or star-like precipitates, the RTP-based phosphorus diffusion technique is efficient for gettering out the precipitated Cu. A two-step RTP gettering process is much more effective than a single-step RTP process. Furthermore, the choice of oxygen ambient can enhance the Cu gettering efficiency due to the involvement of considerable self-interstitial silicon atoms. The minority carrier lifetime of the sample subjected to RTP-based phosphorus gettering has also been verified to be significantly enhanced. These results are of interest for the gettering engineering of high-efficiency silicon solar cells.

Gettering Mechanism of Cu in Silicon Calculated from First Principles

The binding energy between 3d transition metals (TM) such as iron (Fe), nickel (Ni) and copper (Cu), and boron (B) in Si are studied using first-principles molecular dynamics method. The binding energies of between each TM for Fe, Ni, Cu and B are 0.64,0.57,and 0.44eV respectively, and the binding energy of Fe and B is the largest, on the other hand, binding energy of Ni and B is the smallest. This result is well in agreement with the experiment fact that Fe and Cu exist as a positive charge in P+ silicon, so it is easy to combine with the B, which has a negative charge, on the other hand, Ni exists in the state of neutrality electrically in P+ silicon, so it can not combine with B atom.

Formation of the photoluminescence Cu center on in-diffusion and out-diffusion of Cu in dilute Cu-contaminated silicon crystals

Changes of photoluminescence (PL) intensity of the 1.014 eV Cu center (CuPL) with in- and out-diffusion of Cu in dilute Cu-contaminated silicon crystals (∼1013 atom/cm3) were observed. The intensity of CuPL increased with in-diffusion temperature of Cu to 700 °C and then decreased with increasing temperature above 800 °C for a short in-diffusion time. The formation barrier for CuPL (0.65 eV) obtained from the in-diffusion process of Cu below 600 °C was much smaller than the known effective formation enthalpy of an interstitial solution of Cu in silicon from Cu metal plated on silicon (1.5 eV), i.e., CuPL was formed more easily for a dilute Cu-contaminated sample than for a thickly Cu-plated sample. The decrease of the PL intensity of CuPL above 800 °C is attributed to the formation of another, more stable species than CuPL. A part of the in-diffused Cu out-diffused at room temperature after removing the surface oxide of the crystal for p-type crystals. Little change of CuPL intensity occurred on out-diffusion of Cu, indicating that CuPL and the out-diffusing species differed from each other. The changes of CuPL intensity on in- and out-diffusion processes of Cu were reasonably explained by assuming participation of several stable Cu species (at least three) in the silicon crystal.

Diffusion Studies of Cu in Si and Low-k Dielectric Materials

AbstractExperimental results are presented on the diffusion of Cu in silicon and Black Diamond¶ (BD). Cu coated silicon samples, with and without the BD layer, are annealed at various temperatures and times. It is concluded that Cu diffusion in silicon is inhibited in the presence of a copper silicide formed during annealing and/or low solubility at temperatures less than 400°C. On the other hand, the incorporation of Cu in the BD film is observed to be strongly dependant on the method of deposition of the Cu layer. It is further concluded, based on device reliability data, that intentional backside Cu contamination does not pose serious device reliability problems even when subjected to annealing at temperatures typically used for backend processing.

Ultra-fast diffusion mechanism of the late 3d transition metal impurities in silicon

Based upon ab initio electronic structure calculations with super-cells and an FLAPW method, we discuss the mechanism of the ultra-fast diffusion and the reduction of the migration barriers of the late 3d transition atom impurities of Co, Ni and Cu in silicon. The reduction mechanism of the migration barriers of the late 3d transition metal impurities is due to the pseudo-Jahn-Teller interaction, in which the six-fold-coordinated bonds are formed at the interstitial D 3d symmetry site and the energy gain by these bonds overcomes that of the four-fold-coordinated bonds at the tetrahedral T d interstitial site. For Sc, Ti, V, Cr, Mn and Fe impurities in silicon, the T d interstitial site is more stable than the D 3d site, however, for Co, Ni and Cu impurities, the D 3d interstitial site becomes more stable than the T d interstitial site. Calculated migration barriers are in reasonably good agreement with the experimental data. We discuss the systematic variation of the chemical trend of the migration barrier of 3d transition metal impurities in silicon based upon the calculation.

Diffusion, solubility and gettering of copper in silicon

The feasibility of quantitative predictive modeling of gettering of Cu in silicon, which requires quantitative understanding of its diffusivity and precipitation behavior, is discussed. Investigations of diffusion of Cu at low temperatures enabled us to determine the pairing constants of copper with boron, re-evaluate its diffusivity at room temperature in p-Si, and to predict its diffusivity in p +-Si substrates. We demonstrate that copper may either precipitate in the bulk of the wafer or diffuse to its surface, depending on the position of Fermi level in the sample. It is suggested that the Fermi level position determines the sign and magnitude of the electrostatic charge on the growing copper precipitates, and thus enhances or suppresses precipitation of interstitial copper ions. Modeling of p/p + segregation gettering of copper shows that while the copper can be gettered in p + layer during or after high-temperature anneals, it eventually will be released and will precipitate in the device region within the first few months of operation, unless more stable gettering (precipitation) sites for copper are utilized. An n-type layer is predicted to be an effective gettering site.

Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

Comparison of beam‐induced profile broadening effects of gallium and copper in oxygen‐bombarded silicon

AbstractOxygen‐induced profile broadening in secondary ion mass spectrometry (SIMS) has been studied for Ga and Cu in silicon under 10 keV O2+ bombardment at impact angles of 2–82°. A beam‐induced broadening effect was evident for impact angles <30° to the surface normal. In this range of impact angles, the SIMS signal of Cu showed exceptionally long decay, and its decay length decreased with increase in impact angle. By contrast, the decay length of Ga had a maximum at around 27° and decreased below this value. This difference in decay behaviour is attributed to the difference in impurity transport during beam‐induced oxidation. While Cu segregates at the SiO2/Si interface, Ga diffuses rather uniformly in the surface SiO2 layer.

Symmetric lattice distortions around deep-level impurities in semiconductors: Vacancy and substitutional Cu in silicon

A model based on the electrostatic Hellmann-Feynman theorem and an empirical valence-force potential has been used to study breathing-mode distortions around the vacancy and substitutional Cu in silicon. The calculation of the forces driving the distortion is based on a self-consistent calculation of the charge-density perturbation. In both cases considered, the author finds an outward breathing-mode distortion of the lattice. By using a Cubic-harmonics expansion of the charge density, the structure of the forces can be examined. It is found that the outward breathing-mode distortion is caused mainly by the reduced charge anisotropy around the defect, which is a result of the defect-induced deficiency in the number of valence electrons. Distortion amplitudes and the spatial extension of the distortion fields are also calculated for the fully relaxed lattice.(38 refs) (Less)

Quasi bands in Green's-function defect models

A basic difficulty in applying the Green's-function formalism to deep defects in solids is discussed. A cure is provided. It is shown that the conventional Green's-function formalism as applied to point-defect problems is derivable by requiring a dual representation of the defect wave functions both in terms of an expression in "local" basis functions and, independently, in terms of the eigenfunctions of the host-crystal Hamiltonian. It is then shown that this dual representation leads to a fundamental limitation of the method. In contrast to what may have been thought, the defect Green's-function (DGF) method does not become increasingly effective as the defect-induced potential perturbation becomes more localized in coordinate space. In fact, a consequence of this dual representation is that for impurities which are chemically mismatched to the host-crystal atoms a computationally intractable and physically undesirable enormous number of host-crystal eigenfunctions (${10}^{2}$ - ${10}^{4}$) is needed to obtain even modestly accurate defect wave functions, energies, and chemical trends. A new, formally exact approach (the "quasi-band-structure representation") is presented. This approach overcomes the difficulties underlying the dual representation in a simple way. It is based on redefining the zero-order basis set and expanding the defect wave functions in terms of such "quasi band wave functions" rather than by pure host wave functions. The former diagonalize the (finite) matrix of the host-crystal Hamiltonian and include aspects of both host and defect orbitals but need not form eigenstates to the host-crystal Hamiltonian operator. We illustrate this exact method for two analytically solvable models: a parabolic defect potential as well as a transition-atom impurity in a silicon free-electron host crystal. A comparison with the results of the conventional DGF calculation is given. Finally, the method is illustrated for a fully self-consistent calculation for substitutional Cu in silicon using nonlocal pseudopotentials.

ChemInform Abstract: DIFFUSION GETTERING OF AU AND CU IN SILICON

Chemischer InformationsdienstVolume 6, Issue 35 Preparative Inorganic Chemistry ChemInform Abstract: DIFFUSION GETTERING OF AU AND CU IN SILICON R. L. MEEK, R. L. MEEKSearch for more papers by this authorT. E. SEIDEL, T. E. SEIDELSearch for more papers by this authorA. G. CULLIS, A. G. CULLISSearch for more papers by this author R. L. MEEK, R. L. MEEKSearch for more papers by this authorT. E. SEIDEL, T. E. SEIDELSearch for more papers by this authorA. G. CULLIS, A. G. CULLISSearch for more papers by this author First published: September 2, 1975 https://doi.org/10.1002/chin.197535049AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue35September 2, 1975 RelatedInformation

Diffusion Gettering of Au and Cu in Silicon

The gettering of Au and Cu by phosphorus diffused from and sources and by boron diffused from a source has been studied. Samples were intentionally contaminated with moderate to large amounts of Au and Cu to obtain impurity levels above the background level, then gettered and finally examined by ion backscattering. The solubilities of Au and Cu were experimentally measured for phosphorus diffusions at various temperatures. The gettering, using either phosphorus source, was found to take place in the silicon and not in the source glass and the Cu and Au atoms were on lattice sites. Differences in the shapes of the profiles of gettered Au for and diffused sources were found and these are discussed in terms of vacancy enhancement effects. In general, phosphorus diffusion gettering appears to operate by solubility enhancement and ion pairing of substitutional metal acceptors. Boron diffusion gettering is less effective than phosphorus, a result which is consistent with solubility calculations and physical arguments. When the solubility is exceeded new phases are formed. The formation of precipitates for boron diffusions has been studied by electron microscopy.