Hot‐pressed 93% boron nitride wafers when properly oxidized and used as an in situ boron dopant in open‐tube silicon diffusions are capable of providing sheet resistance tolerances of ±1–2% across a silicon wafer and ±4% within a run and from run to run. Although for the experimental conditions studied silicon sheet resistance variations were not expected to be a function of diffusion ambient, ambient flow rate, or source to silicon spacing the contrary was found to be true and the relationships opposite to that intuitively expected. By correlating sheet resistance, impurity profiles, and ellipsometric measurements the observed dependence of sheet resistance vs. ambient, ambient flow rate, and source to silicon spacing is explained in terms of normalSi‐B phase formation.

The structure and composition of silicon oxides thermally grown in HCI/Oz ambients were investigated for various oxidation conditions. Oxides were grown in 6-10 v/o HCl at I150~for times of 15 rain-6 hr. Transmission electron microscopy in conjunction with x-ray microanalysis has indicated the presence of an additional condensed phase at the oxidesilicon interface, which appears after a certain oxidation time has elapsed. Scanning electron microscopy has shown that after further oxidation, a gaseous compound accumulates at the interface, lifting the oxide from the silicon, and preferentially etching the silicon. A model of the growth mechanisms of HCI oxides, accounting for the additional phase formation, is proposed. * Electrochemical Society Student Member. ** Electrochemical Society Active Member.

The sourcing lifetimes, microstructural stability, and diffusion performance of a new solid planar phosphorus source for silicon doping were investigated in the temperature range 900~176The source wafers were highly porous ceramic wafers containing 25 weight percentage (w/o) SiP207 as the "active" component in an inert refractory binder matrix. The microstructural stability and thermogravimetric analysis (TGA) results indicated the structural integrity and sourcing ability of this material at temperatures of at least 1050~C. Theoretical lifetimes of 260 and 3400 hr at 1L00 ~ and 900r reslcectively, have been predicted from the TGA results. Experimental data relating sheet resistance, junction depth, and diffusion coefficient for silicon wafers doped using these source wafers are presented. Special material handling procedures are also described.The results of previous studies concerning the diffusion performance of boron nitride as a p-type dopant source for silicon technology have shown that planar sources offer several significant advantages over carrier gas diffusion systems using liquids and gases (1, 2). The benefits of planar diffusion sources have been previously reported by Goldsmith et al. (3), and it is towards this end that the development and evaluation of the new phosphorus source was aimed. In addition to the benefits presented by Goldsmith et al.,there is the added benefit of having a source material which has no toxic or corrosive by-products.In using boron nitride as a source, the surface is oxidized (activated) to form B203, and the boron is vaporized and transported as an oxide to the silicon surface. An analogous refractory compound of phosphorus which can be fabricated into a ceramic wafer was not available to emulate the boron nitride technology. However, Murata (4) demonstrated that silicon pyrophosphate, SiP2OT, decomposes to SiO2 and P205 with the P205 partial pressure being adequate to effectively dope silicon in the temperature range 850~176In this paper the discussion is confined to a wafer composition of 25 w/o SIP207 in an inert matrix mate-* Electrochemical Society Active Member.

The interrelationship which exists between sodium passivation and phase separation in silicon oxides thermally grown in HC1/O2 ambients was investigated using the capacitance-voltage bias temperature stress technique in conjunction with transmission electron microscopy. Oxides were grown in 0, 3, 6, and i0 volume percent (v/o) HCI for various times at ll00 ~ I150 ~ and 1200~ The threshold in passivation characteristic of these oxides was shown to be a steep portion of a continuous, smooth curve, rather than a sharp discontinuity. The microstructural investigation showed that the development of the additional, chlorine-rich phase correlates well with passivation. The development of this phase, characterized by growth and coalescence, is modeled in terms of phase transformation kinetics.

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The improved electrical stability and accelerated growth kinetics of thermal SiO2 grown in oxygen ambients containing Cl2 and normalHCl have been well documented, but the mechanisms of this improvement are still poorly understood. This paper presents calculations of equilibrium partial pressures of the possible gaseous species in the Cl‐H‐O system under thermal oxidation conditions. These results are correlated with published results on (i) oxidation kinetics; (ii) detrimental effects of water vapor in the growth ambient; and (iii) chlorine content in the as‐grown oxide.

Secondary ion mass spectrometry (SIMS) and electron microscopy have been used to investigate the distribution of hydrogen and chlorine in SiO2 films thermally grown on silicon. These films have been grown in various ambients, including pure O2, steam, HCl/O2, and Cl2/O2, as well as HCl/O2 mixtures diluted with N2. The data suggest that there exists a strong interaction between the chlorine and the hydrogen, with the chlorine being a very effective gettering agent for hydrogen. The results of this investigation, as well as a model explaining the incorporation and distribution of the hydrogen and chlorine, are presented.