D Gräf

Influence of boron concentration on the oxidation-induced stacking fault ring in Czochralski silicon crystals

The influence of the boron doping level in the range of 1 x 10(15)-2 x 10(19) cm(-3) on the position of the oxidation-induced stacking fault ring (R-OSF) in silicon crystals has been investigated by experiments and numerical simulation. For low boron-doped crystals, the position of the R-OSF is described by a critical value C-crit defined by the ratio of the pull rate and the temperature gradient in the crystal at the solid/liquid interface. Boron concentrations higher-than 10(17) cm(-3) shift the position of the R-OSF towards the wafer center without change of growth parameters. The critical value C-crit converts into a function C-crit(C-B), depending linearly on the boron concentration C-B. Crystal-originated particles (COP) and gate oxide integrity (GOI) yield distributions which are consistent with the R-OSF pattern. A low COP density and a high GOI yield are observed outside the ring; a high COP density and a medium GOI yield in the inner region bordered by the ring. It is assumed that boron atoms modify the thermodynamical properties of vacancies and self-interstitials.

Characterization of Crystal Quality by Crystal Originated Particle Delineation and the Impact on the Silicon Wafer Surface

Characterization of Si wafers by delineation of crystal originated particles (COP) provides insight into size and radial distribution of crystal related defects. A good correlation of the COP densities with gate oxide integrity and flow pattern defect densities is observed. The density and size distribution of COP in Czochralski Si ingots can be modified by the pulling rate and the cooling conditions of the crystal and is further influenced by high doping concentrations. The COP densities are comparable on wafers with (100) Si and (111) Si orientation as well as on p- and n-type wafers with moderate doping level. No COP are found on float zone (FZ) and on epitaxially grown wafers. Crystal defects are also delineated by chemomechanical polishing and can be detected on the wafer surface as light point defects (LPD). LPD densities, however, do not necessarily correlate with the corresponding COP densities after SC1 treatment and do not reflect the quality of the crystals because polishing delineates only part of the larger crystal defects to a size which is above the detection limits of commercially available scanning surface inspection systems. High temperature annealing results in reduction of defect sizes and partial dissolution of COP Investigations of FZ and oxygen doped float zone indicate that oxygen is participating in the formation of COP.

Grown‐in Oxide Precipitate Nuclei in Czochralski Silicon Substrates and Their Role in Device Processing

Using a method to study the grown-in defect density spectra in Czochralski silicon wafers, we elucidate the changes in the size distribution of grown-in oxide precipitate nuclei caused by thermal processing in a common complementary metal-oxide semiconductor device process. The first thermal step determines which parts of the grown-in defects grow to large stable defects and how many harmful defects appear in the defect-denuded zone. The cooling rate of the crystal considerably influences the defect evolution during complementary metal oxide semiconductor processing. The choice of appropriate silicon material for a device process or adjusting processing conditions to suit the material are important for defect generation during processing and, consequently, also for device yield.

Influence of Residual Point Defect Supersaturation on the Formation of Grown‐In Oxide Precipitate Nuclei in CZ‐Si

Density spectra of grown-in oxide precipitate nuclei were measured along the radius of a silicon wafer with a stacking fault ring. A first-order approximation model allows us to explain the experimental observations. By fitting growth rate curves to the defect density spectra, the residual point defect supersaturation present during formation of oxide precipitate nuclei can be estimated. We show that the ring region is the region where the vacancy supersaturation remains subcritical and no vacancy agglomeration occurs, resulting in the highest residual vacancy supersaturation, and finally leading to the largest grown-in oxide precipitate nuclei. These nuclei first reach the critical size for stacking fault formation during subsequent thermal treatments.

Erratum to “The impact of nitrogen on the defect aggregation in silicon”: [J. Crystal Growth 226 (2001) 19–30]

We are greatly indebted to V.V. Voronkov of MEMC, who made us aware of an error in our above paper. By mistake, the wrong V=G curve is shown in Fig. 5. The wrong curve relates to older calculations with inappropriate boundary conditions. The below figure shows the correct shape of V=G as determined by calculations which considered inductive heating effects at the circumference of the growing crystal and used the measured growth interface as a boundary condition (see Section 4 on page 23). We apologize for this careless mistake.