High Purity Planar Dopant Sources 

BoronPlus Sources Have High Purity. Page 3

All three BoronPlus diffusion sources are produced from high-purity raw materials. The typical impurity analysis of a melt, when measured on a spark source mass spectrograph is given in Table 1.

Figures 1 and 2 show relative amounts of sodium and iron found on the surfaces of silicon wafers doped with a BoronPlus source, a BN source, and a typical spin-on solution of B₂O₃ detected with a secondary ion mass spectrometer (SIMS). Although absolute amounts of impurities were not determined by this technique, the relative concentrations of impurities can be estimated by comparing the areas under the curves. These data indicate that most of the impurities are strongly tied up in the glassy matrix of the BoronPlus sources and do not evolve at a high rate during use. The result is a relatively pure glassy film of B₂O₃ being deposited on the silicon wafer surface.

Table 1
TYPICAL IMPURITY ANALYSIS OF BoronPlus SOURCE

Metal	PPM	Metal	PPM
Na	2	Pt	<5
K	<1	Rh	<1
Li	<1	As	<0.5
Fe	2	P	<5
Pb	1	Sb	<0.5
Cr	2	Bi	<0.5
Cu	0.5	V	<1
Sn	<0.5	Co	<2
Zn	<2	Mo	1
Ti	2	Ca	20
Ni	2	Sr	20
Ag	<0.5	Mn	<1
Au	<0.5

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