Semiconductor structures including vertical diode structures and methods of making the same
Semiconductor structures and methods of making a vertical diode structure are provided. The vertical diode structure may have associated therewith a diode opening extending through an insulation layer and contacting an active region on a silicon wafer. A titanium silicide layer may be formed over the interior surface of the diode opening and contacting the active region. The diode opening may initially be filled with an amorphous silicon plug that is doped during deposition and subsequently recrystallized to form large grain polysilicon. The silicon plug has a top portion that may be heavily doped with a first type dopant and a bottom portion that may be lightly doped with a second type dopant. The top portion may be bounded by the bottom portion so as not to contact the titanium silicide layer. In one embodiment of the vertical diode structure, a programmable resistor contacts the top portion of the silicon plug and a metal line contacts the programmable resistor.
1. A method for forming a diode, the method comprising:
forming an oxide layer over a semiconductor substrate doped with a first type dopant;
forming a first recess in the oxide layer;
forming a silicon-containing plug in the first recess, the silicon-containing plug being doped with a second type dopant having a conductivity opposite to a conductivity of the first type dopant;
filling the first recess with a second silicon-containing material doped with the first type dopant;
forming a diode junction in the silicon-containing plug with diffused dopants from the second silicon-containing material silicon;
forming a second recess in an active region proximate the first recess, the second recess extending through the oxide layer to expose a portion of the active region of the doped semiconductor substrate;
filling the second recess with a third silicon-containing material doped with the second type dopant; and
forming a programmable resistor in contact with the second silicon-containing material.
2. The method of claim 1 , wherein filling the first recess with a second silicon-containing material comprises filling the first recess with polysilicon.
3. The method of claim 1 , wherein forming a diode junction comprises forming a diode junction by a heat treatment process.
4. The method of claim 1 , further comprising forming a contact on the programmable resistor.
5. The method of claim 1 , wherein forming a first recess in the oxide layer further comprises forming a first recess in a layer of material selected from the group consisting of silicon monoxide, silicon dioxide or silicon nitride.
6. The method of claim 1 , wherein forming a silicon-containing plug further comprises growing an epitaxial silicon layer on an exposed surface of an active region of the doped semiconductor substrate.
7. The method of claim 6 , wherein growing an epitaxial silicon layer comprises growing an epitaxial silicon layer having a thickness of about 1500 Angstroms to about 3000 Angstroms.
8. The method of claim 1 , wherein forming a first recess in the oxide layer comprises simultaneously forming two adjacent holes within a P-minus active region of the doped semiconductor substrate.
9. The method of claim 1 , further comprising forming metal row lines contacting the programmable resistor.
10. The method of claim 9 , further comprising:
depositing a second oxide layer over doped metal row lines;
forming a channel in the second oxide layer to expose the third silicon-containing material;
depositing conductive material in the channel; and
depositing tungsten over the conductive material.
11. The method of claim 10 , wherein the channel has a diameter larger than the second recess.
12. The method of claim 10 , wherein the conductive material is a refractory metal.
13. The method of claim 10 , wherein depositing tungsten further comprises:
depositing a first tungsten layer in the channel;
removing conductive material and the first tungsten layer from the second oxide layer; and
filling the channel with a second tungsten layer.