Variable conducting element and method of programming

• US 5,886,920 A
• Filed: 12/01/1997
• Issued: 03/23/1999
• Est. Priority Date: 12/01/1997
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Anderson, David J., Marshall, Daniel S., Lan, Ellen, Hallmark, Jerald Allen
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): PHAN, TRONG Q
• Application Number:
  US08/982,175
• Time in Patent Office: 477 Days
• Field of Search: 365/65, 365/117, 365/145, 365/149, 257/295
• US Class Current: 365/145
• CPC Class Codes: G11C 11/22 using ferroelectric elements
• CPC Class Codes: G11C 11/223 using MOS with ferroelectric gate insulating film

Abstract

A variable conducting element (10) and method for programming a constant current or constant resistance provided at output terminals (24 and 26) of a ferroelectric transistor (12). The ferroelectric transistor (12) has portions of a ferroelectric material (32A) programmed having up-polarization states separated by domain walls (34) from portions of a ferroelectric material (32B) programmed having down-polarization states. The portion of the ferroelectric material (32A) programmed in the up-polarization state forms current conduction channels between a source region (23) and a drain region (25) of the ferroelectric transistor (12). The ferroelectric transistor (12) is programmed through a capacitor (14) to adjust the charge supplied to a control terminal (22) of the ferroelectric transistor (12).

Claims

1. A variable conducting element, comprising:

a ferroelectric transistor having a control terminal and first and second current carrying terminals;

a select transistor having a control terminal coupled for receiving a select signal and first and second current carrying terminals, wherein the first current carrying terminal is coupled for receiving a control signal; and

a capacitor having a first terminal and a second terminal, wherein the first terminal is coupled for receiving a programming signal and the second terminal is commonly coupled to the control terminal of the ferroelectric transistor and to the second current carrying terminal of the select transistor.

2. The variable conducting element of claim 1, wherein the select transistor is an N-channel field effect transistor.

3. The variable conducting element of claim 1, wherein the ferroelectric transistor is an N-channel field effect transistor structure.

4. The variable conducting element of claim 1, wherein the ferroelectric transistor is a depletion mode transistor.

5. The variable conducting element of claim 1, wherein the select transistor is a depletion mode transistor.

6. A method of programming a variable conducting element, comprising the steps of:

establishing a direct current (D.C.) voltage on a terminal of a gate capacitor of a ferroelectric transistor;

providing a pulse signal through a capacitor to the gate capacitor of the ferroelectric transistor to cause a change in voltage on the gate capacitor of the ferroelectric transistor; and

programming a first portion of a ferroelectric material of the ferroelectric transistor to have an up-polarization state in accordance with the charge transferred to the ferroelectric transistor.

7. The method of claim 6, further comprising the step of providing the D.C. voltage through a transistor to the terminal of the gate capacitor of the ferroelectric transistor.

8. The method of claim 7, further comprising the step of conducting a current in the ferroelectric transistor based on a ratio of the first Dortion of the ferroelectric material of the ferroelectric transistor programmed in the up-polarization state to a second portion of the ferroelectric material programmed in a down-polarization state.

9. A method of programming a ferroelectric transistor, comprising the steps of:

transferring a charge through a conduction path of a transistor to a gate terminal of a ferroelectric transistor, wherein the charge is stored on a gate capacitor of the ferroelectric transistor;

supplying a signal through a capacitor to the gate capacitor of the ferroelectric transistor, wherein the signal alters the charge stored on the gate capacitor of the ferroelectric transistor; and

conducting a current in the ferroelectric transistor based on the charge stored on the gate capacitor of the ferroelectric transistor.

10. The method of claim 9, further comprising the step of providing a select signal to a gate terminal of the transistor for selecting the transistor.

11. The method of claim 10, further comprising the step of deselecting the transistor prior to the step of supplying a signal throuah a capacitor to the gate capacitor of the ferroelectric transistor.