Semiconductor Device Dummy Word Line Biasing for HCI Mitigation
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Solution Overview
Problem
Semiconductor memory devices face challenges in reducing Hot Carrier Injection (HCI) and read disturbance due to lateral electric fields, which affect the reliability and read characteristics of memory cells.
Innovation Solution
The semiconductor device employs a method where a first pass voltage is applied to unselected word lines, with an initial voltage lower than the first pass voltage applied to a dummy word line, and then both voltages are increased to a second pass voltage, setting biases for the word lines and dummy word line to mitigate carrier introduction and reduce HCI, thereby improving read characteristics and data reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pass voltage is applied to unselected word lines to enable sensing operations, then read characteristics are improved, but lateral electric fields are generated causing Hot Carrier Injection and read disturbance
Solution Approach 1:
The dummy memory cell is configured to be turned on before the sensing operation begins, by applying an initial voltage to the dummy word line that is higher than the threshold voltage. This preliminary action prepares the dummy transistor to conduct and establish the potential distribution in advance, preventing carrier injection during the subsequent sensing phase when pass voltages are applied to unselected word lines.
Solution Approach 2:
The dummy memory cell acts as an intermediary element between the selected memory string and the unselected memory strings. By turning on the dummy transistor, it provides an alternative current path and stabilizes the potential at the source/drain region, thereby preventing carriers from being injected into the channel of unselected memory strings during sensing operations.
2Reliability
If biases are set for word lines during sensing operations, then read characteristics are enhanced, but carrier introduction occurs leading to Hot Carrier Injection
Solution Approach 1:
The dummy transistor is activated in advance before the sensing operation starts, by setting the dummy word line voltage higher than the threshold voltage. This preliminary activation establishes the proper potential distribution and prevents carrier injection when pass voltages are subsequently applied to unselected word lines during sensing.
Solution Approach 2:
The dummy memory cell serves as an intermediary that absorbs or redirects the harmful effects of lateral electric fields. By being turned on, it provides a controlled path for charge carriers and stabilizes the electrical environment, preventing carriers from being injected into the channel regions of unselected memory strings.
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 approach effectively mitigates Hot Carrier Injection and read disturbance, enhancing the reliability and read characteristics of semiconductor memory devices by controlling the biases of word lines and dummy word lines during sensing operations.
Implementation Method 1
Semiconductor memory devices face challenges in reducing Hot Carrier Injection (HCI) and read disturbance due to lateral electric fields
Implementation Method 2
Semiconductor memory devices face challenges in reducing Hot Carrier Injection (HCI) and read disturbance due to lateral electric fields
Data Source
AI summary
A semiconductor device and method of operating a semiconductor device, the semiconductor device includes memory strings coupled between a common source line and a bit line, and a peripheral circuit coupled to the memory strings through a plurality of word lines and a dummy word line, and configured to set bias of the word lines and the dummy word line before performing a read operation, wherein the peripheral circuit applies a first pass voltage to the word lines concurrently with applying an initial voltage lower than the first pass voltage to the dummy word line, and increases the first pass voltage and the initial voltage to a second pass voltage to set the bias of the word lines and the dummy word line.