PRAM Heating Electrode with Positive Temperature Coefficient
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Solution Overview
Problem
Phase change random access memory (PRAM) devices require high temperatures for programming, leading to high power consumption and difficulties in integration due to the need for wide MOS transistors and large cell areas.
Innovation Solution
A PRAM design incorporating a heating electrode made of materials with a positive temperature coefficient, such as barium titanate, which increases specific resistance with temperature, allowing for efficient heat supply with reduced programming current by exploiting high resistance at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high temperature heating is applied to convert phase change material state, then phase change is achieved, but power consumption increases significantly
Solution Approach 1:
The patent changes the electrical resistance parameter of the heating electrode by selecting materials with positive temperature coefficient (PTC) characteristics. As temperature increases, the electrode's resistance increases, which automatically limits the current and reduces power consumption at high temperatures while maintaining effective heating capability.
Solution Approach 2:
The heating electrode with PTC characteristics provides self-regulating heating. When the temperature reaches a certain level, the increased resistance automatically reduces the power input, preventing overheating and reducing overall power consumption without requiring external control mechanisms.
2Power
If channel width of MOS transistor is widened to supply high program currents, then sufficient current for phase change is achieved, but cell area increases
Solution Approach 1:
The patent changes the electrical resistance parameter of the heating electrode by selecting materials with positive temperature coefficient (PTC) characteristics. As temperature increases, the electrode's resistance increases, which automatically limits the current and reduces power consumption at high temperatures while maintaining effective heating capability.
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 design reduces power consumption and enables high integration by minimizing the programming current while maintaining low resistance for swift read operations, thus achieving low power consumption and efficient programming.
Implementation Method 1
the heating electrode is formed of a material having a positive temperature coefficient such that specific resistance of the material increases with temperature
Implementation Method 2
PRAM devices use Joule (ohmic) heating to set the state of its phase change materials
Implementation Method 3
A phase change random access memory (PRAM) is a memory device that uses a material that changes its phase, e.g., amorphous to crystalline, as a mechanism to store data
Data Source
AI summary
A PRAM and method of forming the same are disclosed. In various embodiments, the PRAM includes a lower insulation layer formed on a semiconductor substrate, a phase change material pattern formed on the lower insulation layer and a heating electrode contacting the phase change material pattern. The heating electrode can be formed of a material having a positive temperature coefficient such that specific resistance of the material increases as a function of temperature.