Experimental study of the boron redistribution in bilayer films silicon-based by SIMS technique
The present work focuses on the study two sets of films bilayers obtained by Low Pressure Chemical Vapor Deposition (LPCVD), for use as material to MOS gate structures (transistors, chemical sensor ISFET, etc.). The first series of films are composed by two layers, silicon amorphous un-doped layer (poly1) and polysilicon boron doped in situ (poly2). The second series are constituted by boron doped polysilicon (polySi) and nitrogen doped polysilicon (NIDOS). These films (poly1/poly2 and polySi/NIDOS) are annealed in tem the same conditions of deposit and annealing. The boron concentration is monitored by secondary ion mass spectrometry (SIMS). The superposition between the SIMS profiles of poly1/poly2 and polySi/NIDOS films have shown that low thermal annealing budget at 600°C/2h, ensures long boron redistribution to the interface poly2/SiO2. At the contrary, a high thermal budget the second layer (poly2) was recristallyzed and reached to the doped oxide. For polySi/NIDOS films, SIMS profiles confirmed the presence of low nitrogen (X = 1%) which can effectively suppress the boron penetration at the interface NIDOS/SiO2.
Boron doped polysilicon deposition in a sector reactor : Specific phenomena and properties
In this paper, the advantages of a new LPCVD reactor, called sector reactor, are presented. This reactor is a small scale pilot plant of an annular reactor, designed to solve the problem of uniformity of thickness observed in tubular reactors. This work describes the deposition of in situ Boron doped Silicon from BCl 3 and SiH 4 . The kinetic results shows that the use of the sector reactor allows deposition at temperature as low as 450°C, pressure as high as 6Torr, deposition rates as high as 80nm/mn, keeping the homogeneity of thickness and resistivity at a good level on 10cm substrates. The kinetic and resistivity results are compared to what is obtained in conventional furnace, and are interpreted in terms of gas phase reactions. Finally, the advantage of processing at low temperature ( 0.5μm).
Diffusion characteristics of boron and phosphorus in polycrystalline silicon
Abstract Grain boundary diffusion of dopants (boron and phosphorous) in silicon is discussed. The appropriate models and equations are presented both for semi-infinite and for thin film boundary conditions. Data reported in the literature for both thick and thin samples have generally been analyzed using models appropriate to diffusion in a homogeneous semi-infinite substrate. These data were reanalyzed using the appropriate boundary conditions and a more realistic model of the inhomogeneous nature of diffusion in polycrystalline samples. It was shown that, even though the relation between diffusion depth and time may be the same from bulk and grain boundary models, the diffusion coefficients determined from assuming the homogeneous semi-infinite solid may be several orders of magnitude in error for the pre-exponential factor, and the activation energy will also be wrong. Grain boundary diffusion coefficients for arsenic, boron and phosphorus in silicon were determined.