Virtual ground sensing circuitry and related devices, systems, and methods for crosspoint ferroelectric memory

• US 10,438,644 B2
• Filed: 11/08/2018
• Issued: 10/08/2019
• Est. Priority Date: 05/20/2015
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Marotta, Giulio Giuseppe, Tiburzi, Marco Domenico
• Primary Examiner(s): Leboeuf, Jerome
• Application Number:
  US16/184,719
• Publication Number:
  US 20190096465A1
• Time in Patent Office: 334 Days
• CPC Class Codes: G11C 11/221 using ferroelectric capacitors
• CPC Class Codes: G11C 11/2253 Address circuits or decoders
• CPC Class Codes: G11C 11/2273 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/5657 using ferroelectric storage elements
• CPC Class Codes: G11C 2213/77 Array wherein the memory element being directly connected to the bit lines and word lines without any access device being used
• CPC Class Codes: G11C 7/062 Differential amplifiers of non-latching type, e.g. comparators, long-tailed pairs
• CPC Class Codes: G11C 7/067 Single-ended amplifiers

Abstract

Virtual ground sensing circuits, electrical systems, computing devices, and related methods are disclosed. A virtual ground sensing circuit includes a sense circuit configured to compare a reference voltage potential to a sense node voltage potential, and virtual ground circuitry operably coupled to the sense circuit. The virtual ground circuitry is configured to provide a virtual ground at a first bias voltage potential to a conductive line operably coupled to a selected ferroelectric memory cell, and discharge the conductive line to the sense node responsive to the selected ferroelectric memory cell changing from a first polarization state to a second polarization state. A method includes applying a second bias voltage potential to another conductive line operably coupled to the selected ferroelectric memory cell, and comparing a sense node voltage potential to a reference voltage potential. Electrical systems and computing devices include virtual ground sensing circuits.

Claims

1. A method of operating an electrical system, the method comprising:

applying, with biasing circuitry, a critical voltage potential to a selected ferroelectric memory cell in an array of ferroelectric memory cells through a pair of conductive lines operably coupled to the selected ferroelectric memory cell, wherein the critical voltage potential is selected to cause the selected ferroelectric memory cell to switch from a first polarization state to a second polarization state;

discharging, with virtual ground sensing circuitry operably coupled to one of the pair of conductive lines, charge that is at least one of sinked to and emitted from the selected ferroelectric memory cell to a sense node if the selected ferroelectric memory cell switches from the first polarization state to the second polarization state, wherein the sense node has a sense node capacitance that is less than a capacitance of the one of the pair of conductive lines; and

detecting a polarization state of the selected ferroelectric memory cell responsive to a voltage change at the sense node, wherein a ratio of the voltage change at the sense node to a voltage change on one of the conductive lines is inversely proportional to a ratio of the sense node capacitance to the capacitance of the one of the pair of conductive lines.

2. The method of claim 1, further comprising determining that the selected ferroelectric memory cell was in the first polarization state responsive to detecting the charge that is discharged to the sense node.

3. The method of claim 1, further comprising determining that the selected ferroelectric memory cell was in the second polarization state responsive to detecting zero change in charge at the sense node.

4. The method of claim 1, further comprising determining that the selected ferroelectric memory cell was in a third polarization state different from the first polarization state and the second polarization state responsive to detecting a different charge that is discharged to the sense node.

5. A computing device, comprising:

a memory device including;

an array of ferroelectric memory cells; and

control circuitry including a virtual ground sensing circuit configured to;

selectively operably couple to the array of ferroelectric memory cells;

provide a virtual ground to a conductive line operably coupled to a selected ferroelectric memory cell;

selectively operably couple the conductive line to a sense node of a sense circuit responsive to the selected ferroelectric memory cell switching from a first polarization state to a second polarization state, the sense node having a sense node capacitance less than a capacitance of the conductive line; and

capacitively couple the sense node to a low voltage potential power supply, wherein responsive to the ferroelectric memory cell switching from a first polarization state to a second polarization state, a ratio of a voltage change on the sense node to a voltage change on the conductive line is inversely proportional to the ratio of the sense node capacitance to the capacitance of the conductive line; and

a processing circuit operably coupled to the memory device, the processing circuit configured to execute computer-readable instructions stored in the array of ferroelectric memory cells.

6. The computing device of claim 5, further comprising at least one input device and at least one output device operably coupled to the processing circuit, and configured to enable a user of the computing device to interact with the computing device.

7. The computing device of claim 5, wherein the sense node capacitance and the capacitance of the conductive line are selected such that a voltage change on the sense node is larger than a voltage change on the conductive line.

8. The computing device of claim 5, wherein one or more of the sense node capacitance and the capacitance of the conductive line is a parasitic capacitance.

9. The computing device of claim 5, wherein one or more of the sense node capacitance and the capacitance of the conductive line is a capacitor.

10. A control circuit comprising:

a virtual ground sensing circuit configured to;

provide a virtual ground to a conductive line;

selectively operably couple the conductive line to a sense node of a sense circuit, the sense node having a sense node capacitance less than a capacitance of the conductive line;

compare a sense node voltage to a reference voltage; and

sense a change in voltage of the sense node, wherein the change in voltage at the sense node is defined by a ratio of the change in voltage at the sense node to a change in voltage at the conductive line, wherein a ratio of the change in voltage at the sense node to the change in voltage at the conductive line is inversely proportional to the ratio of the sense node capacitance to the capacitance of the conductive line.

11. The control circuit of claim 10, wherein the sense node capacitance is less than about 1 picoFarad.

12. The control circuit of claim 10, further comprising a power supply capacitively coupled to the sense node.

13. The control circuit of claim 10, wherein the change in voltage at the conductive line is between 200 microvolts (μ

V) and 500 microvolts (μ

V).

14. The control circuit of claim 10, wherein at least one of the sense node capacitance and the capacitance of the conductive line is defined by a capacitor.