Method of forming sloped members of N-type polycrystalline silicon

A method of forming a conductive member of N-type and high conductivity polycrystalline silicon on a surface of an insulating substrate with at least one side thereof sloping gradually to said surface of the insulating substrate comprising

• forming a layer of polycrystalline silicon on said surface of the insulating substrate,
• forming a region of N-type and high conductivity including boron impurities in a concentration in excess of about 10.sup.18 atoms per cubic centimeter and extending from the exposed surface of said layer of polycrystalline silicon to the opposite surface thereof, said region having at least one generally planar side portion, said side portion of said region gradually sloping from the exposed surface of said layer of polycrystalline silicon to the opposite surface thereof and making a small acute angle with the base of said region lying on said surface of the insulating substrate,
• etching said layer of polycrystalline silicon with an etch which etches polycrystalline silicon containing boron impurities in excess of said concentration at a rate substantially less than the rate at which it etches polycrystalline silicon not containing boron impurities for a period of time to remove the portion of said layer of polycrystalline silicon not containing boron in excess of said concentration,
• whereby said region of said polycrystalline layer remains to provide said conductive member on said insulating substrate.