3D stacked high-density memory cell arrays and methods of manufacture
Integrated circuit devices having multiple level arrays of thyristor memory cells are created using a stack of ONO layers through which NPNPNPN layered silicon pillars are epitaxially grown in-situ. Intermediate conducting lines formed in place of the removed nitride layer of the ONO stack contact the middle P-layer of silicon pillars. The silicon pillars form two arrays of thyristor memory cells, one stacked upon the other, having the intermediate conducting lines as common connections to both arrays. The stacked arrays can also be provided with assist-gates.
1. The integrated circuit device having a plurality of thyristor memory cell arrays, the device comprising:
a set of first parallel conducting lines;
a set of second parallel conducting lines;
an array of semiconductor pillars, the pillars having layers of alternating polarity, first and second end layers at first and second ends of the pillars having the same polarity and a middle layer of opposite polarity, each first end of a semiconductor pillar connected to a first parallel conducting line and each second end of a semiconductor pillar connected to a second parallel conducting line;
a set of parallel intermediate conducting lines, each middle layer of a semiconductor pillar connected to an intermediate conducting line so that the semiconductor pillar forms a first thyristor between a first parallel conducting line and the intermediate conducting line, and a second thyristor between a second parallel conducting line and the intermediate conducting line;
whereby the first thyristor of the semiconductor pillar comprises part of a first thyristor memory cell array and the second thyristor of the semiconductor pillar comprises part of a second thyristor memory cell array below the first thyristor memory cell array.
2. The integrated circuit device of claim 1 wherein the semiconductor pillars comprise epitaxially grown semiconductor material.
3. The integrated circuit device of claim 2 wherein the semiconductor material comprises silicon, silicon germanium or a combination of silicon and silicon germanium.
4. The integrated circuit device of claim 2 wherein the layers of alternating polarity of the semiconductor pillars comprise in-situ doped epitaxially grown semiconductor material.
5. The integrated circuit device of claim 1 further comprising:
a first set of assist-gate electrodes electrically coupled to base regions of the thyristor memory cells of the first thyristor memory cell array; and
a second set of assist-gate electrodes electrically coupled to base regions of the thyristor memory cells of the second thyristor memory cell array.
6. The integrated circuit device of claim 5 wherein the first set of assist-gate electrodes comprises:
a first set of polysilicon lines parallel to the set of intermediate conducting lines, and between the set of first conducting lines and the set of intermediate conducting lines; and the second set of assist-gate electrodes comprises:
a second set of polysilicon lines parallel to the set of intermediate conducting lines, and between the set of second conducting lines and the set of intermediate conducting lines.
7. The integrated circuit device of claim 1 comprising:
a set of third parallel conducting lines;
a set of fourth parallel conducting lines;
a second array of semiconductor pillars, the pillars having layers of alternating polarity, first and second end layers at first and second ends of the pillars having the same polarity and a middle layer of opposite polarity, each first end of a semiconductor pillar connected to a third parallel conducting line and each second end of a semiconductor pillar connected to a fourth parallel conducting line;
a set of second parallel intermediate conducting lines, each middle layer of a semiconductor pillar connected to a second intermediate conducting line so that the semiconductor pillar forms a third thyristor between a third parallel conducting line and the intermediate conducting line, and a fourth thyristor between a fourth parallel conducting line and the intermediate conducting line, the third thyristor of the semiconductor pillar comprising part of a third thyristor memory cell array and the fourth thyristor of the semiconductor pillar comprising part of a fourth thyristor memory cell array below the third thyristor memory cell array, the fourth thyristor memory cell array stacked upon the first thyristor memory cell array;
whereby a four level stack of thyristor memory cell arrays is formed.