Semiconductor memory device having unequal pitch vertical channel transistors employed as selection transistors and method for programming the same
A semiconductor device comprises a set of selection transistors, such as in a three-dimensional memory structure or stack having resistance change memory cells arranged along vertical bit lines. Each selection transistor has a non-shared control gate and a shared control gate. The transistor bodies may have an unequal pitch and a common height. Some of the transistor bodies can be misaligned with the vertical bit lines to fit the transistors to the stack. A method for programming the three-dimensional memory structure includes forming one or two channels in a transistor body to provide a current to selected memory cells. Programming can initially use one channel and subsequently use two channels based on a programming progress. A method for fabricating a semiconductor device includes etching a gate conductor material so that shared and non-shared control gates have a common height.
1. A method for programming in a three-dimensional memory structure, comprising:
supplying a first voltage to a first horizontal bit line on a substrate, wherein:
the three-dimensional memory structure is above the first horizontal bit line, the three-dimensional memory structure comprising first and second vertical bit lines, memory cells arranged along the first vertical bit line and memory cells arranged along the second vertical bit line;
a first selection transistor is arranged between the first horizontal bit line and the first vertical bit line, the first selection transistor comprises a first vertical channel transistor body, a first control gate and a second control gate, and the first control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal bit line; and
a second selection transistor is arranged between the first horizontal bit line and the second vertical bit line, the second selection transistor comprises a second vertical channel transistor body, the second control gate as a shared control gate which is shared with the first selection transistor, and a third control gate, the third control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal bit line; and
wherein the first vertical channel transistor body is misaligned with the first vertical bit line, and the second vertical channel transistor body is misaligned with the second vertical bit line,
during the supplying the first voltage to the first horizontal bit line, supplying a second voltage to the first control gate which is sufficient to form a conductive channel through the first vertical channel transistor body as part of one conductive path between the first horizontal bit line and the first vertical bit line.
2. The method of claim 1 , further comprising, during the supplying the first voltage to the first control gate and the supplying the first voltage to the first horizontal bit line:
initially supplying a third voltage to the second control gate which is insufficient to form a conductive channel through either of the first and second vertical channel transistor bodies;
determining a programming progress of one or more memory cells of the memory cells arranged along the first vertical bit line; and
based on the programming progress, supplying a fourth voltage to the second control gate which is sufficient to form another conductive channel through the first vertical channel transistor body as part of another conductive path between the first horizontal bit line and the first vertical bit line.
3. The method of claim 2 , wherein:
the determining the programming progress comprises determining whether programming has been completed by a specified program-verify cycle for the one or more memory cells of the memory cells arranged along the first vertical bit line.
4. The method of claim 2 , wherein:
the determining the programming progress comprises determining whether a specified number of the one or more memory cells arranged along the first vertical bit line have completed programming after a specified program-verify cycle.
5. The method of claim 1 , further comprising, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal bit line:
supplying a third voltage to the third control gate which is insufficient to form a conductive channel through the second vertical channel transistor body.
6. The method of claim 1 , further comprising, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal bit line:
supplying a third voltage to the second control gate which is insufficient to form a conductive channel through either of the first and second vertical channel transistor bodies.
7. The method of claim 1 , further comprising, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal bit line:
supplying a third voltage to the second control gate which is sufficient to form another conductive channel through the first vertical channel transistor body as part of another conductive path between the first horizontal bit line and the first vertical bit line.
8. The method of claim 1 , wherein:
the programming comprises programming one or more of the memory cells arranged along the first vertical bit line without programming one or more of the memory cells arranged along the second vertical bit line.
9. An apparatus, comprising:
a substrate;
a first horizontal conductive line on the substrate;
a three-dimensional memory structure above the first horizontal conductive line, the three-dimensional memory structure comprising first and second vertical conductive lines, memory cells arranged along the first vertical conductive line and memory cells arranged along the second vertical conductive line;
a first selection transistor arranged between the first horizontal conductive line and the first vertical conductive line, the first selection transistor comprises a first vertical channel transistor body, a first control gate and a second control gate, and the first control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal conductive line;
a second selection transistor arranged between the first horizontal conductive line and the second vertical conductive line, the second selection transistor comprises a second vertical channel transistor body, the second control gate as a shared control gate which is shared with the first selection transistor, and a third control gate, the third control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal conductive line; and
a control circuit, the control circuit, during a programming operation, is configured to:
supply a first voltage to the first horizontal conductive line; and
wherein the first vertical channel transistor body is misaligned with the first vertical conductive line, and the second vertical channel transistor body is misaligned with the second vertical conductive line,
during the supplying the first voltage to the first horizontal conductive line, supply a second voltage to the first control gate which is sufficient to form a conductive channel through the first vertical channel transistor body as part of one conductive path between the first horizontal conductive line and the first vertical conductive line.
10. The apparatus of claim 9 , wherein:
the memory cells arranged along the first vertical conductive line and the memory cells arranged along the second vertical conductive line comprise resistance change memory cells.
11. The apparatus of claim 9 , wherein during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal conductive line, the control circuit is configured to:
initially supply a third voltage to the second control gate which is insufficient to form a conductive channel through either of the first and second vertical channel transistor bodies;
determine a programming progress of one or more memory cells of the memory cells arranged along the first vertical conductive line; and
based on the programming progress, supply a fourth voltage to the second control gate which is sufficient to form another conductive channel through the first vertical channel transistor body as part of another conductive path between the first horizontal conductive line and the first vertical conductive line.
12. The apparatus of claim 9 , wherein, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal conductive line, the control circuit is configured to:
supply a third voltage to the third control gate which is insufficient to form a conductive channel through the second vertical channel transistor body.
13. The apparatus of claim 9 , wherein, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal conductive line, the control circuit is configured to:
supply a third voltage to the second control gate which is insufficient to form a conductive channel through either of the first and second vertical channel transistor bodies.
14. The apparatus of claim 9 , wherein, during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal conductive line, the control circuit is configured to:
supply a third voltage to the second control gate which is sufficient to form another conductive channel through the first vertical channel transistor body as part of another conductive path between the first horizontal conductive line and the first vertical conductive line.
15. The apparatus of claim 9 , wherein:
the control circuit, during the programming operation, is configured to program one or more of the memory cells arranged along the first vertical conductive line without programming one or more of the memory cells arranged along the second vertical conductive line.
16. The apparatus of claim 9 , wherein:
the three-dimensional memory structure comprises alternating conductive layers and dielectric layers arranged along the first and second vertical conductive lines; and
during the supplying the second voltage to the first control gate and the supplying the first voltage to the first horizontal conductive line, the control circuit is configured to supply a first voltage to one or more of the conductive layers.
17. An apparatus, comprising:
a first horizontal conductive line on a substrate;
a memory structure above the first horizontal conductive line, the memory structure comprising alternating conductive layers and dielectric layers, first and second vertical conductive lines, memory cells arranged along the first vertical conductive line and memory cells arranged along the second vertical conductive line;
a first transistor arranged between the first horizontal conductive line and the first vertical conductive line, the first transistor comprises a first vertical channel transistor body, a first control gate and a second control gate, and the first control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal conductive line;
a second transistor arranged between the first horizontal conductive line and the second vertical conductive line, the second transistor comprises a second vertical channel transistor body, the second control gate as a shared control gate which is shared with the first transistor, and a third control gate, the third control gate is not shared with any other vertical channel transistor body which is arranged along the first horizontal conductive line;
wherein the first vertical channel transistor body is misaligned with the first vertical conductive line, and the second vertical channel transistor body is misaligned with the second vertical conductive line,
means for supplying a first voltage to the first horizontal conductive line; and
means for, during the supplying the first voltage to the first horizontal conductive line, supplying a second voltage to the first control gate which is sufficient to form a conductive channel through the first vertical channel transistor body as part of one conductive path between the first horizontal conductive line and the first vertical conductive line.
18. The apparatus of claim 17 , further comprising:
means for supplying a third voltage to the second control gate which is insufficient to form a conductive channel through either of the first and second vertical channel transistor bodies;
means for determining a programming progress of one or more memory cells of the memory cells arranged along the first vertical conductive line; and
means for, based on the programming progress, supplying a fourth voltage to the second control gate which is sufficient to form another conductive channel through the first vertical channel transistor body as part of another conductive path between the first horizontal conductive line and the first vertical conductive line.