Clamping Unit Prevents Latch Up in Semiconductor Memory
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Solution Overview
Problem
The latch up phenomenon in CMOS inverters of semiconductor memory devices leads to increased power consumption, malfunction, and potential destruction due to parasitic bipolar junction transistors, and existing methods to prevent it are ineffective in reducing power consumption and area without altering manufacturing parameters.
Innovation Solution
A semiconductor memory device with a clamping unit that controls the source voltage to a level lower than the bulk bias, preventing the latch up by managing the voltage levels of PMOS and NMOS transistors, thereby reducing power consumption and preventing device malfunction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a CMOS inverter structure with neighboring NMOS and PMOS transistors is used, then device integration is achieved, but latch up phenomenon occurs causing increased power consumption and potential device destruction
Solution Approach 1:
A clamp transistor is introduced as an intermediary component between the NMOS and PMOS transistors. This clamp transistor monitors the voltage difference between the two transistors and activates to block the latch-up current path when excessive current is detected, thereby preventing the harmful feedback loop while maintaining the integrated CMOS structure.
Solution Approach 2:
The clamp transistor implements a feedback mechanism by continuously monitoring the voltage relationship between NMOS and PMOS transistors. When the voltage difference exceeds a threshold indicating potential latch-up conditions, the clamp transistor activates to suppress the parasitic bipolar junction transistor current, creating a negative feedback loop that prevents device destruction.
2Reliability
If conventional latch up prevention methods are used, then some protection is achieved, but power consumption is not reduced and device area increases
Solution Approach 1:
The clamp transistor changes the voltage parameters dynamically by adjusting its conduction state based on the real-time voltage difference between NMOS and PMOS transistors. When latch-up conditions are detected, the clamp transistor modifies the voltage distribution to suppress parasitic current, achieving protection without requiring continuous high power consumption.
Solution Approach 2:
The clamp transistor acts as a protective element that remains inactive during normal operation and only activates temporarily when latch-up conditions occur. This allows the use of a simple, low-cost transistor structure that provides effective protection only when needed, rather than requiring complex continuous protection circuits that consume power constantly.
3Ease of manufacture
If parasitic bipolar junction transistors are present in the CMOS structure, then device fabrication is simplified, but latch up occurs causing device malfunction and destruction
Solution Approach 1:
The invention converts the harmful effect of parasitic bipolar junction transistors into a detectable signal. The voltage difference caused by these parasitic transistors serves as an indicator that triggers the clamp transistor activation, transforming the harmful parasitic effect into a useful monitoring mechanism that prevents device destruction.
Solution Approach 2:
The clamp transistor is positioned and configured to preemptively block the latch-up current path before the parasitic bipolar junction transistors can cause device destruction. By monitoring voltage differences and activating in advance, the clamp transistor prevents the harmful feedback loop from establishing, countering the parasitic effect before it becomes catastrophic.
Data Source
AI summary
A semiconductor memory device employs a clamp for preventing latch up. For the purpose, the semiconductor memory device includes a precharging/equalizing unit for precharging and equalizing a pair of bit lines, and a control signal generating unit for producing a control signal which controls enable and disable of the precharging/equalizing unit, wherein the control signal generating unit includes a clamping unit to clamp its source voltage to a voltage level lower than that of its bulk bias.