Process for forming a planar diode using one mask
View Patent ↗A planar diode and method of making the same employing only one mask. The diode is formed by coating a substrate with an oxide, removing a central portion of the oxide to define a window through which dopants are diffused. The substrate is given a Ni/Au plating to provide ohmic contact surfaces, and the oxide on the periphery of the window is coated with a polyimide passivating agent overlying the P/N junction.
1. A diode comprising:
(a) a substrate of a first conductivity type and a doped region of a second conductivity type defining a P/N junction therebetween;
(b) nickel plating on the underside of the substrate and along a central portion of a top side of the substrate overlying the doped region of the second conductivity type;
(c) an oxide coating on the peripheral portion of the top side of the substrate adjacent the central portion; and
(d) a coating of a passivating material along the oxide on the top side of the substrate, the passivating material extending partially over the P/N junction,
wherein the nickel plating does not overlap with the oxide coating on the peripheral portion of the top side of the substrate.
2. The diode of claim 1 , wherein said first conductivity type has N-type conductivity and said second conductivity type has P-type conductivity.
3. The diode of claim 1 , wherein said doped region is doped with boron.
4. The diode of claim 1 , wherein the passivating material is polyimide.