EP0615247A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
A ferroelectric memory cell and method of sensing and writing the polarization state thereof
Assignee: Motorola Solutions Inc
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Filing: 1994-03-03
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Granted: —
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Expires: 2014-03-03
Abstract
Abstract A memory cell (10) containing a ferroelectric capacitor (20) the memory state of which is sensed by cycling the potential across the capacitor from zero, through an upper electric field point (C) and back to zero. If the cell was residing in the upper permanent remnant polarization point (D), a low change in charge flow occurs and if the cell was residing in the lower permanent remnant polarization point (A), a low (near zero) change in charge flow occurs. This change in charge flow from a near zero value to a large amount allows a very accurate reference capacitor (39) to be used for the comparison or sensing process.
Inventors
- 👤 Howard C. Kirsch
- 👤 Papu D. Maniar
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 11:26
CPC Classifications
G; G11; G11C; G11C11/00; G11C11/21; G11C11/22; G11C11/225; G11C11/221
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
84 words
A method of sensing the polarization state of a ferroelectric memory cell (10) including a ferroelectric capacitor (20) having a hysterisis curve with upper and lower electric field points (C, F) and upper and lower permanent remnant polarization points (D, A), the method characterized by the steps of: applying an electric field to the ferroelectric capacitor, which electric field is cycled from zero to substantially one of the upper and lower electric field points and back to zero; and measuring a change in polarization.
Claim 2
Dependent Claim
39 words
The method of claim 1 further characterized in that the step of measuring a change in polarization includes measuring a change in charge that flows into the ferroelectric capacitor as a result of the cycling of the electric field.
Claim 3
Dependent Claim
32 words
The method of claim 2 further characterized in that the step of measuring a change in polarization includes comparing the measured change in charge to a charge on a reference capacitor (39).
Claim 4
Dependent Claim
29 words
The method of claim 3 further characterized in that the step of measuring a change in polarization includes providing a charge on a reference capacitor (39) which is fixed.
Claim 5
Dependent Claim
145 words
A ferroelectric memory cell and associated reference cell characterized by: a ferroelectric memory cell (10) including a ferroelectric capacitor (20), the ferroelectric capacitor having a hysterisis curve with upper and lower electric field points (C, F) and upper and lower permanent remnant polarization points (D, A) and always residing in one of the upper and lower permanent remnant polarization points; a reference cell (12) having a reference capacitor (39); means (22, 23) attached to the memory cell for cycling the ferroelectric capacitor between substantially zero electric potential thereacross, an electric potential sufficient to move the polarization to one of the upper and lower electric field points and back to substantially zero electric potential; and means (30) attached to the ferroelectric cell and the reference cell for comparing electric charge flowing into the ferroelectric capacitor during the cycling to an electric charge in the reference capacitor.
Claim 6
Dependent Claim
62 words
A ferroelectric memory cell and associated reference cell as claimed in claim 5 further characterized in that the means attached to the memory cell for cycling the ferroelectric capacitor is designed to cycle the ferroelectric capacitor between substantially zero electric potential, an electric potential sufficient to move the polarization to the upper electric field point and back to substantially zero electric potential.
Claim 7
Dependent Claim
62 words
A ferroelectric memory cell and associated reference cell as claimed in claim 5 further characterized in that the means attached to the memory cell for cycling the ferroelectric capacitor is designed to cycle the ferroelectric capacitor between substantially zero electric potential, an electric potential sufficient to move the polarization to the lower electric field point and back to substantially zero electric potential.
Claim 8
Dependent Claim
52 words
A ferroelectric memory cell and associated reference cell as claimed in claim 5 further characterized in that the reference capacitor is designed to provide an electric charge which is equal to a largest postulated polarization change of the ferroelectric capacitor plus a margin for worst case imbalance of the means for comparing.
Claim 9
Dependent Claim
30 words
A ferroelectric memory cell and associated reference cell as claimed in claim 5 further characterized in that the reference capacitor includes one of a ferroelectric capacitor and a linear capacitor.
References Cited (Backward Citations)
No citation records indexed.
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