Diffusion of dopant from optical coating and single step formation of PN junction in silicon solar cell and coating thereon
AssigneeWestinghouse Electric Corp.
InventorsBulent E. Yoldas, Lubomyra A. Yoldas
Life of this patent
Estimating the term…
Abstract
The PN juncture in a silicon chip and an oxide coating on its surface are simultaneously formed from clear solution derived from titanium alkoxides, water, alcohol, a suitable acid, and a P or N dopant compound by partial hydrolysis and polymerization. The solution is applied to the surface of a silicon chip. The chip is then heated which converts the solution to a solid oxide coating which meets the antireflective optical film requirements and induces the migration of the dopants into the chip, forming a PN junction in the chip. The method also provides deep and uniform junction formation or diffusion without resulting in excessive carrier concentration.
Claims20
A method of doping silicon comprising forming a coating on said silicon from an alkoxide solution partially hydrolyzed with water, where at least 40% of said coating is titania, said coating containing a dopant selected from the group consisting of boron and phosphorus, and heating said coated silicon above the diffusion temperature of said dopant, thereby diffusing said dopant into said silicon.
The clear solution which results from mixing ingredients comprising:
- (A) alkoxide having the general formula M(OR).sub.n where M is selected such that an oxide coating formed from this solution is selected from the group consisting of 40 to 100% TiO.sub.2, 0 to 25%, SiO.sub.2, and up to 15% of another metal oxide of a metal which forms an alkoxide, and mixtures thereof, R is alkyl from C.sub.1 to C.sub.6, and n is the valence of M;
- (B) about 1.7 to about 8 moles of water per mole of alkoxide;
- (C) sufficient alcohol to give a solid content of about 0.1 to about 15%;
- (D) a sufficient amount of a suitable acid to prevent cloudiness;
- and
- (E) about 1% to about 50% of a dopant compound selected from the group consisting of boron and phosphorus containing compounds.
A method of simultaneously doping a silicon chip and forming an oxide coating on its surface comprising:
- (A) preparing the clear solution which results from mixing ingredients comprising:
- (a) alkoxide having the general formula M(OR).sub.n where M is selected such thut an oxide coating formed from this solution is selected from the group consisting of 40 to 100% TiO.sub.2, 0 to 25% SiO.sub.2, and up to 15% of another metal oxide of a metal which forms an alkoxide, and mixtures thereof, R is alkyl from C.sub.1 to C.sub.6, and n is the valence of M;
- (b) about 1.7 to about 8 moles of water per mole of alkoxide;
- (c) sufficient alcohol to give a solid content of about 0.1 to about 15%;
- (d) a sufficient amount of a suitable acid to prevent cloudiness;
- and
- (e) about 1% to about 50% of a P or N dopant compound selected from the group consisting of boron and phosphorus containing compounds;
- (B) applying said solution to the surface of said chip;
- and
- (C) heating said chip to convert said solution to a solid coating and to diffuse said dopant into said silicon chip.
Dependencies are inferred from the claim text.