Diode Isolated DENMOS ESD Cell With Grounded Guard Element
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Solution Overview
Problem
Existing voltage protection structures in integrated circuits face challenges in increasing holding voltage while maintaining a desired trigger voltage, as methods like increasing lateral spacing or diode area lead to undesirable area expansion.
Innovation Solution
Incorporating a guard element coupled to ground, proximate to the diode and DENMOS transistor, with a heavily doped p-type region, and optimizing the guard element's configuration to manage hole injection and substrate potential, thereby providing a desired holding voltage without increasing the structure's area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lateral spacing between diode and DENMOS is increased or diode area is increased, then holding voltage is improved, but area of voltage protection structure deteriorates
Solution Approach 1:
A guard ring structure is introduced as an intermediary element between the diode and DENMOS transistor. The guard ring comprises a guard ring well and guard ring doping regions that act as a mediator to enhance holding voltage by controlling substrate potential distribution, thereby achieving improved holding voltage without increasing the overall protection structure area.
Solution Approach 2:
The guard ring introduces localized doping regions with different doping types and concentrations in specific areas around the diode and DENMOS transistor. This creates local variations in electrical properties (substrate potential control) without changing the overall structure dimensions, enabling enhanced holding voltage while maintaining compact area.
2Reliability
If lateral spacing between diode and DENMOS is increased or diode area is increased, then holding voltage is improved, but trigger voltage control deteriorates
Solution Approach 1:
The guard ring serves as an intermediary that decouples the relationship between diode-DENMOS spacing and holding voltage. By introducing the guard ring doping regions as a separate control mechanism, the trigger voltage can be independently optimized while the guard ring parameters (doping concentration, distribution) control the holding voltage, thus resolving the trade-off between trigger voltage control and holding voltage enhancement.
Solution Approach 2:
The protection structure is segmented into functionally distinct regions: the diode-DENMOS trigger path and the guard ring holding voltage control path. This segmentation allows independent optimization of trigger voltage (through diode-DENMOS parameters) and holding voltage (through guard ring parameters), eliminating the coupled trade-off present in conventional structures.
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 effectively enhances the holding voltage of the voltage protection structure while minimizing the overall area, providing a balanced solution to the challenge of maintaining trigger voltage and structural size.
Implementation Method 1
A guard element is disposed between the diode and the DENMOS transistor. The guard element is coupled to ground. The guard element includes a heavily doped p-type region
Data Source
AI summary
An integrated circuit contains a voltage protection structure having a diode isolated DENMOS transistor with a guard element proximate to the diode and the DENMOS transistor. The guard element includes an active area coupled to ground. The diode anode is connected to an I/O pad. The diode cathode is connected to the DENMOS drain. The DENMOS source is grounded. A process of forming the integrated circuit is also disclosed.