Metal Gate Diode ESD Protection Reducing Self-Heating
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Solution Overview
Problem
Polysilicon gated diode ESD protection devices experience high self-heating due to low thermal conductivity and heat capacity, leading to reduced robustness in semiconductor integrated circuits, particularly at 14 nanometer technology nodes and beyond.
Innovation Solution
A metal gated diode protection device is formed with a metal gate made of tungsten (W) or aluminum (Al) having high thermal conductivity and heat capacity, which acts as a heat sink to reduce self-heating, using a replacement metal gate (RMG) process and forming n-type and p-type regions through specific source/drain processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon gate is used in ESD protection device, then low on-state resistance and fast turn-on are achieved, but high self-heating occurs due to low thermal conductivity and heat capacity
Solution Approach 1:
The patent changes the material parameter of the gate from polysilicon to metal (such as tungsten or aluminum), which fundamentally alters the thermal conductivity and heat capacity parameters. This material substitution enables the gate to dissipate heat more effectively during ESD events, reducing self-heating while maintaining the required electrical characteristics for ESD protection.
Solution Approach 2:
The invention creates a composite structure where a metal gate is integrated with the semiconductor substrate and ESD protection diode. The metal gate layer (5-200 nm thick) forms a composite with the underlying polysilicon or semiconductor material, combining the low on-state resistance and fast turn-on of the original structure with the high thermal conductivity and heat capacity of the metal layer to achieve both electrical performance and thermal management.
2Temperature
If metal gate is used to reduce self-heating, then thermal conductivity and heat capacity are improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the metal gate layer early in the manufacturing process, before the ESD protection diode structures are fully formed. The metal gate is deposited and patterned first, then subsequent processing steps (forming n-type and p-type regions, creating sidewall spacers) are performed around it. This preliminary placement simplifies integration compared to adding metal gates later in the process.
Solution Approach 2:
The metal gate acts as an intermediary element that mediates between the electrical requirements (low on-state resistance) and thermal requirements (heat dissipation) of the ESD protection device. It serves as a thermal conduit connecting the heat-generating junction to the substrate, while simultaneously functioning as the control electrode for the diode, thus simplifying the overall device architecture by combining multiple functions in a single element.
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
The metal gated diode significantly reduces self-heating, enhancing the robustness of ESD protection and maintaining high current shunting capabilities, as demonstrated by lower temperature increases during electrostatic discharge compared to polysilicon gates.
Implementation Method 1
metal having high κ and high CV... acts as a heat sink to reduce self-heating
Implementation Method 2
metal having high κ and high CV... lower temperature increases during electrostatic discharge
Data Source
AI summary
A method of forming a metal gate diode ESD protection device and the resulting device are provided. Embodiments include forming a metal gate diode including a metal gate on a substrate; forming an n-type cathode on a first side of the metal gate diode; and forming a p-type anode on a second side of the metal gate diode, opposite the first side.