Complementary PCRAM Cell Structure for High Read Margin
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Solution Overview
Problem
The 1T-1R phase change random access memory (PCRAM) cells have a small read margin due to the need for a reference signal, which limits their performance.
Innovation Solution
A semiconductor structure is developed with two phase change memory structures configured in complementary states, where the first phase change memory structure's bottom electrode is connected to a transistor's first terminal, and the second phase change memory structure's top electrode is connected to the same terminal, eliminating the need for an external reference signal, thereby enhancing read speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 1T-1R PCRAM cell structure is used, then the memory cell can be randomly and independently selected, but the read margin is small due to the need for a reference signal
Solution Approach 1:
The memory cell is segmented into two distinct phase change memory structures (first PCRAM structure and second PCRAM structure) that operate in complementary states. Each structure has its own electrode connections to the transistor, allowing independent control and read operations without requiring external reference signals.
Solution Approach 2:
The invention changes the operational parameter state by utilizing complementary phases (crystalline and amorphous) of the phase change material in the two structures. One structure is maintained in crystalline phase while the other is in amorphous phase, creating inherent signal differentiation that eliminates the need for reference signals.
2Reliability
If two phase change memory structures are configured in complementary states with shared transistor connection, then the read margin and reliability are improved, but the device structure becomes more complex
Solution Approach 1:
Two phase change memory structures are merged by sharing a common transistor and connecting their electrodes to the same transistor terminal. This merging approach allows both structures to operate simultaneously in complementary states while using shared control circuitry, improving read margin without proportionally increasing overall device complexity.
Solution Approach 2:
The shared transistor serves multiple functions by controlling both the first and second phase change memory structures. The single transistor can selectively access either structure for read or write operations, providing multi-functionality that reduces the need for additional control components.
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 configuration achieves a high read margin and reliability by allowing the semiconductor structure to operate without an external reference signal, improving read speed and reliability.
Implementation Method 1
the phase change material presents different resistivity during rapid and reversible conversion between a crystalline phase and an amorphous phase under the effect of Joule heat of an electric current
Implementation Method 2
under the effect of Joule heat of an electric current
Data Source
AI summary
The present disclosure relates to a semiconductor structure and a manufacturing method thereof. The semiconductor structure includes a transistor; a first phase change memory structure, a bottom electrode of the first phase change memory structure being electrically connected to a first terminal (source or drain) of the transistor; a second phase change memory structure, a top electrode of the second phase change memory structure being electrically connected to the first terminal of the transistor; a first bit line, electrically connected to a top electrode of the first phase change memory structure; and a second bit line, electrically connected to a bottom electrode of the second phase change memory structure.