Diode-Connected DRAM Cell for Parasitic Capacitance
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Solution Overview
Problem
Dynamic Random Access Memory (DRAM) devices face challenges in shrinking memory cell area due to parasitic capacitance, leading to charge loss and increased power consumption from frequent transistor switching to refresh data.
Innovation Solution
A semiconductor device and circuit design that includes a diode and a transistor connected to a capacitor, where the diode turns on when the voltage at the node between the capacitor and diode is lower than a threshold, triggering the transistor to pull up the voltage and refresh the data automatically, reducing the need for frequent transistor switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the memory cell area is shrunk, then the integration density is improved, but parasitic capacitance increases causing charge loss
Solution Approach 1:
A diode is introduced as an intermediary component between the capacitor and the transistor. The diode acts as a mediator that enables automatic voltage equalization and charge recovery, preventing charge loss through parasitic capacitance while maintaining the shrunk memory cell area. The diode's one-way conduction property allows it to redirect current flow to compensate for charge leakage without requiring additional active switching.
Solution Approach 2:
The memory cell structure is designed to be self-service by incorporating the diode that automatically detects and compensates for voltage drops caused by parasitic capacitance. When voltage at the capacitor node drops below the diode threshold, the diode automatically conducts to equalize voltage, eliminating the need for external intervention or frequent manual refreshing operations.
2Reliability
If frequent transistor switching is used to refresh data, then data retention is improved, but power consumption increases
Solution Approach 1:
The diode is pre-configured in the circuit to automatically perform the voltage equalization action before significant charge loss occurs. By setting up the diode's threshold voltage to match the parasitic capacitance effect, the system performs preliminary compensation for voltage drops, preventing the need for frequent transistor switching and reducing power consumption while maintaining data retention.
Solution Approach 2:
The diode provides self-service by automatically detecting when voltage drops below the threshold and initiating voltage equalization without requiring external control signals or frequent transistor switching. This self-regulating mechanism maintains data retention while minimizing power consumption by only activating when necessary.
3Area of moving object
If word line spacing is reduced, then integration density is improved, but parasitic capacitance increases
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitance into a beneficial feature by using the diode to exploit voltage drops caused by parasitic capacitance for automatic voltage equalization. Instead of treating parasitic capacitance as a purely negative factor, the design uses the resulting voltage changes to trigger the diode's protective action, transforming the harmful charge leakage effect into a signal for automatic compensation.
Solution Approach 2:
The diode serves as an intermediary that mediates between the capacitor and the rest of the circuit, specifically addressing the harmful parasitic capacitance effect. It intercepts voltage drops caused by parasitic capacitance and redirects current flow to equalize voltage, preventing the harmful effects from propagating while maintaining reduced word line spacing for high integration density.
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 automatically refreshes data in DRAM cells, reducing power consumption and minimizing charge loss, thereby enhancing the efficiency and reliability of memory cell operations.
Implementation Method 1
When the voltage at the node between the capacitor and the diode is lower than a threshold voltage, the diode will turn
Implementation Method 2
A Dynamic Random Access Memory (DRAM) device is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit
Data Source
AI summary
A semiconductor device and a circuit are provided. The semiconductor device includes a substrate, a first gate structure, a first doped region, and a capacitor structure. The substrate includes a first well region having a first conductive type. The first gate structure is disposed on the substrate. The first doped region is in the substrate and has a second conductive type different from the first conductive type. The first gate structure and the first doped region are included in a first transistor. The capacitor structure includes a first electrode electrically coupled to the first doped region. The second doped region is in the substrate and has the second conductive type. The second doped region is electrically coupled to the first electrode of the capacitor structure and the first doped region.