Etch Rate Characterization of Borosilicate Glasses as Diffusion Sources

Abstract

For diffusion of boron into silicon from a doped oxide diffusion source, the surface concentration of boron in silicon and B2O3 in the glass at the glass‐silicon interface are independent of diffusion time. In the temperature range studied, the surface concentrations are also independent of temperature and depend only on the dopant concentration in the deposited glass. This dependence is observed as long as the glass thickness is large enough so that the impurity source approximates a semi‐infinite source. The concentration dependence of the diffusion coefficients of the B2O3 in the glass and the boron in silicon are determined, the diffusion coefficient for boron in silicon being about 100 times that of the diffusion in the oxide. Heating under an oxidizing ambient oxidizes the silicon at the silicon‐glass interface with the thickness growth rate of the undoped SiO2 layer being nearly independent of the original glass thickness. No such interface barrier to the boron diffusion process occurs when argon is used as an ambient.

Devitrification Kinetics and Mechanism of K2O–CaO–SrO–BaO–B2O3–SiO2 Glass‐Ceramic

“…To obtain the apparent activation energy of crystallization, the k values listed in Table II are 33,34 and 320 -550 kJ/mol, 24 respectively. Only the activation energies of alkaline and alkali ions are close to those needed for the formation of cristobalite and pseudowollastonite, indicating a diffusion-controlling mechanism.…”

“…Another possibility is that the phase transformation is controlled by diffusion of alkaline and alkali ions in glass. Extensive literature search results showed that the activation energies needed for the diffusivity of Ca, Sr, Ba, K, B, and Si in silicate glasses are in the range of 175-295, [22][23][24][25] 165-255, 26 -28 175, 29 165-215, 30 -32 345, 33,34 and 320 -550 kJ/mol, 24 respectively. Only the activation energies of alkaline and alkali ions are close to those needed for the formation of cristobalite and pseudowollastonite, indicating a diffusion-controlling mechanism.…”

Water Vapor as an Oxidant in BBr3 Open-tube Silicon Diffusion Systems

“…The depth in the silicon below this original surface is denoted by y. We in silicon, k «: Dl so that No~N; We expect NJC i to be approximately 0.05 [6]. Graphs of F and G are given by Crank [4].…”

“…The diffusion 1 length 2 (Dt)2 associated with the process is, using t = 1 1 0 1/6 hand D? = 0.01~m-h-2 [6], simply 80 A. Since this is somewhat smaller than the total oxide thickness observed, the formation of a barrier layer of that order of magnitude during oxidation is quite plausible.…”

“…as about 1.7 X 10-3 /otm-h-t for the penetration of boron through thermal Si0 2 at 1050°C, while Schwenker [6] gets approximately 10-2 ILm-h-t for diffusion in vapor-deposited BSG containing approximately 10% B Z0 3 • From the literature [8,9], one obtains a value of k, the parabolic rate constant for oxide growth, of 0.65 I ILm-h-'. Hence, for the conditions of our third run, with a partial pressure of H 20 equal to 7.3 x 10-3 atrn, one ] may estimate k = 0.06 ILm-h-'.…”