Charge Pump Programming for Resistance-Switching Memory
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Solution Overview
Problem
Programming non-volatile memory devices that utilize reversible resistance-switching materials is challenging due to difficulties in controlling the switching between resistance states, leading to unstable operations and potential oscillation between states.
Innovation Solution
A system and method for programming non-volatile storage elements by controlling the amount of charge or energy provided, using a circuit that generates a limited amount of charge or energy over a predetermined number of clock cycles to set and reset the resistance-switching elements, ensuring they are programmed to a desired state without oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sufficient voltage is applied to switch the resistance state, then the material switches to the desired resistance state, but the material may oscillate between states and fail to stabilize
Solution Approach 1:
A charge pump circuit is introduced as an intermediary device between the voltage source and the resistance-switching material. The charge pump delivers a precisely controlled amount of charge to the material, acting as a mediator that prevents direct application of excessive voltage which would cause oscillation. This intermediary mechanism ensures the material transitions to the desired state without overshooting or oscillating.
Solution Approach 2:
The invention changes the control parameter from direct voltage application to controlled charge delivery. By using a charge pump to deliver a specific quantity of charge (Q = C × ΔV) over a predetermined number of clock cycles, the system precisely controls the electrical parameter applied to the material, preventing the material from receiving excessive energy that would cause unstable oscillation between resistance states.
2Productivity
If unlimited charge is provided to program the storage element, then the programming speed increases, but the resistance state becomes unstable and oscillates
Solution Approach 1:
The charge pump circuit implements partial action by delivering only the precise amount of charge needed for programming, rather than continuously applying voltage. The pump operates for a predetermined number of clock cycles to deliver exactly Q = C × ΔV charge, which is sufficient to program the element but limited enough to prevent oscillation. This controlled partial charging achieves both speed and stability.
Solution Approach 2:
The charge pump operates periodically through discrete clock cycles rather than continuously. Each clock cycle delivers a controlled charge increment, and the pump stops after a predetermined number of cycles. This periodic, pulsed charge delivery allows the material to stabilize between charge events and prevents the continuous energy input that would cause oscillation, while still achieving programming within a finite time period.
3Reliability
If high voltage is applied to ensure programming, then programming reliability improves, but the risk of oscillation between resistance states increases
Solution Approach 1:
The invention changes the control parameter from voltage magnitude to charge quantity. Instead of applying high voltage that risks causing oscillation, the charge pump delivers a precisely controlled charge Q = C × ΔV at a controlled rate over predetermined clock cycles. This parameter transformation maintains programming reliability by ensuring sufficient charge is delivered while preventing the excessive voltage conditions that trigger harmful oscillation between resistance states.
Solution Approach 2:
The charge pump serves as an intermediary that decouples the relationship between voltage source and resistance-switching material. It takes the voltage input and transforms it into controlled charge delivery, mediating the energy transfer to the material. This intermediary mechanism ensures reliable programming by delivering sufficient charge while filtering out the voltage excursions that would cause oscillation, thereby eliminating the harmful effect without sacrificing programming reliability.
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
The approach effectively prevents undesirable switching between states during programming, ensuring reliable operation of non-volatile storage elements by limiting the charge or energy supplied, thereby stabilizing the resistance-switching process.
Implementation Method 1
a first circuit that generates charge in response to receiving a clock signal, and a second circuit that runs the first circuit for a predetermined number of clock cycles to generate an amount of charge
Implementation Method 2
A variety of materials show reversible resistance-switching behavior. These materials include chalcogenides, carbon polymers, perovskites, and certain metal oxides and nitrides
Data Source
AI summary
A memory system includes a substrate, control circuitry on the substrate, a three dimensional memory array (above the substrate) that includes a plurality of memory cells with reversible resistance-switching elements, and a circuit for detecting the setting and resetting of the reversible resistance-switching elements. In one aspect a circuit that has one or more clock inputs is run for a predetermined number of clock cycles. The circuit generates an amount of charge over the predetermined number of clock cycles. At most the amount of charge is provided to non-volatile storage element to program the non-volatile storage element. It is determined whether the non-volatile storage element is programmed to a desired state as a result of providing at most the amount of charge to the non-volatile storage element. Techniques disclosed herein can be applied to program memory cells other than memory cells with reversible resistance-switching elements.