Magnetic Memory Cell Voltage Pump and Body Biasing

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Solution Overview

Problem

Conventional magnetic RAMs face challenges in achieving higher density due to large write currents, leakage current issues, and asymmetric current symmetry, which limit their use in smaller memory applications and increase power consumption.

Innovation Solution

The system employs a method and system for magnetic memory cells using a silicon on oxide transistor with a voltage pump to provide a bias voltage greater than the supply voltage, enhancing write current and symmetry, and utilizing body biasing to reduce leakage current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional magnetic RAM uses spin transfer effect with localized phenomenon, then write current is reduced for smaller magnetic elements, but current symmetry becomes asymmetric and leakage current increases

Engineering Contradiction:

Improvewrite currentVSAvoidcurrent symmetry

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies asymmetry by intentionally introducing a resistance asymmetry element in series with the magnetic element. This resistance asymmetry compensates for the inherent current symmetry issues in spin transfer effect-based magnetic RAM, ensuring that write currents in opposite directions are balanced and preventing half-select write disturb problems.

Inventive Principle:

Principle #4Asymmetry

2Quantity of substance

If magnetic element size is reduced for higher density, then write current decreases, but leakage current from selection device becomes more significant

Engineering Contradiction:

Improvememory densityVSAvoidleakage current

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a resistance asymmetry element as an intermediary component in series with the magnetic element. This intermediary element helps manage and balance the current flow, reducing the impact of leakage current from the selection device while maintaining the benefits of smaller magnetic element sizes for higher density.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If selection device is made larger to support higher write current, then current capacity increases, but cell area increases reducing density

Engineering Contradiction:

Improvewrite current capacityVSAvoidcell area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The patent applies local quality by introducing a resistance asymmetry element that is strategically placed in series with the magnetic element. This localized modification allows the selection device to operate at lower current levels while maintaining adequate write current capacity, thereby reducing the required selection device size and cell area without sacrificing write current capability.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for higher write currents and more symmetric current operation, enabling smaller, denser magnetic memory designs with reduced power consumption and improved performance.

Implementation Method 1

a voltage pump coupled with the plurality of magnetic storage cells and the voltage supply. The voltage pump provides a bias voltage to the selection device. The bias voltage is based on the supply voltage and has a magnitude greater than the supply voltage

Methodology Applied

Scientific EffectVoltage pump: Pump

Implementation Method 2

providing a body bias voltage to the body of the transistor. The body bias voltage is a first voltage when the transistor is off and a second voltage when the transistor is on

Methodology Applied

Scientific EffectBody biasing:

Implementation Method 3

The current is spin polarized when passing through the magnetic element 12 and changes the state of the magnetic element 12 by the spin transfer effect. When the current density is sufficiently large, the current carriers driven through the magnetic element 12 may impart sufficient torque to change the state of the magnetic element 12

Methodology Applied

Scientific EffectSpin transfer effect:

Data Source

PatentUS7515457B2Current driven memory cells having enhanced current and enhanced current symmetry

Publication Date: 2009.04.07 SAMSUNG SEMICONDUCTOR INC

AI summary

A method and system for providing and using a magnetic memory is described. The method and system include providing a plurality of magnetic storage cells. Each magnetic storage cell includes a magnetic element and a selection device coupled with the magnetic element. The magnetic element is programmed by write currents driven through the magnetic element in a first or second direction. In one aspect, the method and system include providing a voltage supply and a voltage pump coupled with the magnetic storage cells and the voltage supply. The voltage supply provides a supply voltage. The voltage pump provides to the selection device a bias voltage having a magnitude greater than the supply voltage. Another aspect includes providing a silicon on oxide transistor as the selection device. Another aspect includes providing to the body of the transistor a body bias voltage that is a first voltage when the transistor is off and a second voltage when the transistor is on.