Large array of upward pointing p-i-n diodes having large and uniform current
View Patent ↗An upward-pointing p-i-n diode formed of deposited silicon, germanium, or silicon-germanium is disclosed. The diode has a bottom heavily doped p-type region, a middle intrinsic or lightly doped region, and a top heavily doped n-type region. The top heavily doped p-type region is doped with arsenic, and the semiconductor material of the diode is crystallized in contact with an appropriate silicide, germanide, or silicide-germanide. A large array of such upward-pointing diodes can be formed with excellent uniformity of current across the array when a voltage above the turn-on voltage of the diodes is applied. This diode is advantageously used in a monolithic three dimensional memory array.
1. A first device level formed above a substrate comprising a plurality of vertically oriented p-i-n diodes, each p-i-n diode comprising a bottom heavily doped p-type region, a middle intrinsic or lightly doped region, and a top heavily doped n-type region, wherein each p-i-n diode has the form of a pillar,
wherein, for at least 99 percent of the p-i-n diodes, current flowing through the p-i-n diodes when a voltage between about 1.5 volts and about 3.0 volts is applied between the bottom heavily doped p-type region and the top heavily doped n-type region is at least 1.5 microamps,
wherein the p-i-n diodes comprise deposited silicon, germanium, or silicon-germanium,
wherein the first plurality of p-i-n diodes includes every p-i-n diode in the first device level.
2. The first device level of claim 1 wherein current flowing through the p-i-n diodes when the voltage applied between the bottom heavily doped p-type region and the top heavily doped n-type region is between about 1.8 volts and about 2.2 volts.
3. The first device level of claim 1 wherein each diode is in contact with a silicide, germanide, or silicide-germanide layer.
4. The first device level of claim 3 further comprising:
a first plurality of substantially parallel, substantially coplanar rail-shaped conductors formed above the substrate; and
a second plurality of substantially parallel, substantially coplanar rail-shaped conductors formed above the first conductors, each first p-i-n diode vertically disposed between one of the first conductors and one of the second conductors.
5. The first device level of claim 4 wherein the plurality of vertically oriented p-i-n diodes includes at least 100,000 p-i-n diodes.
6. The first device level of claim 1 wherein a second device level is monolithically formed above the first.
7. The first device level of claim 1 wherein the substrate comprises monocrystalline silicon.