Dome-Shaped PCM Mushroom Cell for Lower SET/RESET Current
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Solution Overview
Problem
Existing non-volatile random-access memory (NVRAM) technologies require constant power to retain data, limiting their use in applications requiring data retention without power, such as faster boot times, and lack efficient thermal insulation for reduced SET/RESET current.
Innovation Solution
The creation of dome-shaped phase change memory mushroom cells with a reduced contact area between the top metal electrode and phase change material, utilizing a dielectric surrounding the phase change material to enhance thermal insulation, and incorporating airgaps to minimize thermal dissipation, thereby reducing the SET/RESET current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the contact area between the top electrode and the phase change material is reduced, then thermal insulation is improved, but the electrical connection reliability may deteriorate
Solution Approach 1:
The patent applies local quality by creating a dome-shaped PCM structure where the contact area between the top electrode and PCM is reduced at the top region while maintaining adequate contact at the base region. This localized modification of the contact interface allows improved thermal insulation at the electrode-PCM interface without compromising the overall electrical connection reliability through the heater structure.
Solution Approach 2:
The patent employs spheroidality by forming the phase change material into a dome-shaped structure rather than a flat layer. This curved geometry naturally reduces the contact area between the top electrode and the PCM, thereby improving thermal insulation while the dome's base maintains sufficient electrical connection through the heater.
2Use of energy by moving object
If the contact area between the top electrode and the phase change material is reduced, then SET/RESET current is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes phase transitions by forming the dome-shaped PCM structure through controlled phase change material deposition and transformation. This process allows the formation of the desired dome geometry with reduced top contact area while managing the manufacturing precision requirements through the material's phase transition behavior during fabrication.
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 proposed solution enables improved thermal insulation and reduced current requirements for SET/RESET operations, enhancing the efficiency and effectiveness of phase change memory cells in retaining data without constant power and improving thermal management.
Implementation Method 1
applying an electrical current to a bottom electrode of a memory cell, increasing a temperature, based on the applied electrical current, of a heater electrically connected to the bottom electrode
Implementation Method 2
forming an amorphous dome in a shaped phase change material (PCM) thermally and electrically connected to the heater based on the increasing temperature of the heater
Data Source
AI summary
A mushroom memory cell may be formed by depositing a second dielectric layer on top of a first dielectric layer and a heater, depositing a hard mask on top of the second dielectric layer, performing a directional reactive-ion etching to remove an exposed portion of the second dielectric layer, performing a lateral etching to remove a portion of the second dielectric layer under the hard mask, performing directional deposition of a phase change material (PCM) over the heater, depositing a covering dielectric over the PCM, performing a second directional etching to expose a top surface of the PCM, and depositing a top electrode on the surface of the PCM.