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Hot-pressed solid diffusion sources for phosphorus
| Details |
Inventors: Myles, Thomas A.; Zimmer, Curtis E.;
Assignee: The Carborundum Company (Niagara Falls, NY)
Primary Examiner: Ozaki; G.
Assistant Examiner:
Attorney, Agent or Firm: Dougherty; David E., Green; Raymond W., Mylius; Herbert W.
Solid diffusion sources for phosphorus doping comprise from 10 to 95 percent SiP.sub.2 O.sub.7 with an inert phase of ZrP.sub.2 O.sub.7. Such materials may be hot-pressed to obtain diffusion source wafers of the appropriate dimensions and porosity. A preferred composition comprises from 25 to 75 weight percent SiP.sub.2 O.sub.7, the balance ZrP.sub.2 O.sub.7. Fabrication parameters range from about 750 psi to about 6,000 psi pressure during hot-pressing, at temperatures from about 800.degree.C to about 1450.degree.C. |
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DETAILED DESCRIPTION OF THE INVENTION The solid phosphorus-containing diffusion sources of this invention are prepared in the form of thin circular disks by hot-pressing a blend of finely divided particles of SiP.
sub.
2 O.
sub.
7 and ZrP.
sub.
2 O.
sub.
7, at a suitably elevated temperature and pressure.
The body thus formed comprises essentially pure SiP.
sub.
2 O.
sub.
7 with an inert phase of essentially pure ZrP.
sub.
2 O.
sub.
7.
The formed hot-pressed body is then cut, using known methods such as diamond sawing, to the desired disc thickness.
It has been found quite necessary to minimize any presence of the compound Si.
sub.
2 P.
sub.
2 O.
sub.
9 [(SiO.
sub.
2).
sub.
2 .
P.
sub.
2 O.
sub.
5 ] to obtain a porous body having the necessary structural integrity and sourcing capability.
In the past, phosphorus doping sources have been prepared using SiP.
sub.
2 O.
sub.
7 (with or without Si.
sub.
2 P.
sub.
2 O.
sub.
9), with a high melting additive material, such as zirconium oxide, which has a melting point in excess of 2000.
degree.
C.
Such materials were prepared in accordance with the teachings of U.
S.
patent application Ser.
No.
374,706, filed June 28, 1973, now U.
S.
Pat.
No.
3,852,086 by hot-pressing a slug of blended particles and cutting, such as with a diamond saw, to the desired thickness.
SiP.
sub.
2 O.
sub.
7 and ZrP.
sub.
2 O.
sub.
7 can be prepared as disclosed in copending U.
S.
patent application Ser.
No.
548,118, filed Feb.
7, 1975, by Myles and Zimmer.
The bodies of diffusion material of the present invention may be fabricated in graphite molds, using hot-pressing techniques.
Fabrication may be done at temperatures ranging from about 800.
degree.
to 1450.
degree.
C and under pressure ranging from about 750 to 6000 psi.
Holding times in the molds may range from about 15 minutes to 10 hours and the fabrication may be carried out in air, under inert atmospheres such as nitrogen or argon, or under vacuums up to 10.
sup.
-.
sup.
7 Torr.
The choice of fabrication conditions is, of course, governed by the composition of the starting materials used and the conditions under which the resulting diffusion material will be used
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Nonmetallic Processes 
