SiC Barrier Metal Structure for Threshold Voltage Stability
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face issues with cracks in the barrier metal due to internal stress, leading to fluctuations in threshold voltage, especially when the barrier metal is thicker and has a two-layer structure with different materials, causing thermal stress and crack propagation.
Innovation Solution
A silicon carbide semiconductor device with a two-layer barrier metal structure where the lower layer is thinner and made of the same metallic material as the upper layer, preventing crack propagation and hydrogen ion entry into the gate insulating film, thereby stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the barrier metal is made thicker to prevent threshold voltage fluctuations, then the protection against metallic material diffusion is improved, but the barrier metal becomes more prone to cracks due to internal stress
Solution Approach 1:
The barrier metal is divided into a two-layer structure with a first barrier metal layer (thinner, lower stress) and a second barrier metal layer (thicker, higher stress). This segmentation allows each layer to have optimized thickness for its specific function while collectively providing both protection and crack resistance.
Solution Approach 2:
Different regions of the barrier metal structure have different thicknesses and materials optimized for their local functions. The first layer near the gate insulating film is thinner to reduce stress at the critical interface, while the second layer is thicker to provide overall protection, creating local quality variations that resolve the contradiction.
2Reliability
If a two-layer barrier metal structure with different materials is used, then the functional performance is improved, but thermal stress causes cracks between the layers
Solution Approach 1:
The first and second barrier metal layers are made of the same metallic material (e.g., both titanium), ensuring homogeneous thermal expansion properties. This eliminates thermal stress at the interface between layers while maintaining the functional benefits of the two-layer structure through controlled thickness variations.
3Ease of manufacture
If the single-layered barrier metal is made thinner to reduce manufacturing complexity, then the ease of manufacture is improved, but cracks propagate more easily into the interlayer insulating film
Solution Approach 1:
The first barrier metal layer acts as a cushioning layer positioned between the interlayer insulating film and the second barrier metal layer. This prior cushioning prevents crack propagation from the second layer into the insulating film, providing beforehand protection against the harmful effects of cracking.
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 two-layer barrier metal structure effectively prevents cracks and fluctuations in threshold voltage, enhancing the device's reliability and productivity by maintaining strong interatomic bonding and reducing thermal stress.
Implementation Method 1
Since the first and second barrier metals are made of the same metallic material, interatomic bonding between the first and second barrier metals is stronger than that when the first and second barrier metals are made of different metallic materials.
Implementation Method 2
the first barrier metal of the lower layer prevent the cracks, and prevents propagation of the cracks into the interlayer insulating film... prevents hydrogen ions causing fluctuations in threshold voltage from entering a gate insulating film
Implementation Method 3
when the barrier metal has the two-layer structure using different materials, thermal stress caused by a difference in coefficient of thermal expansion is applied between the first and second layers
Data Source
AI summary
The object of a silicon carbide semiconductor device according to the present disclosure is to prevent fluctuations in threshold voltage and prevent cracks in a barrier metal. A silicon carbide semiconductor device includes: a silicon carbide substrate; a semiconductor layer formed on the silicon carbide substrate; a gate electrode facing the semiconductor layer through a gate insulating film; an interlayer insulating film covering the gate electrode; a barrier metal formed on the interlayer insulating film; and a top electrode covering the barrier metal, wherein the barrier metal has a two-layer structure of a barrier metal and a barrier metal, and the barrier metal closer to the interlayer insulating film is made of a same metallic material as the barrier metal, the barrier metal being thinner than the barrier metal.