Trench Semiconductor Contact Structure With Dual Work Function Metals
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Solution Overview
Problem
Existing semiconductor devices with trench gate structures face challenges in reducing contact resistance to decrease on-resistance.
Innovation Solution
The semiconductor device employs a first metallic film with a high work function metal and a second metallic film with a low work function metal, forming an ohmic junction with the third semiconductor layer and a Schottky junction with the second semiconductor layer, respectively, to reduce contact resistance without increasing n-type impurity concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trench contact structure is used to decrease on-resistance, then contact resistance must be reduced, but conventional single-metal structures cannot achieve sufficiently low contact resistance without increasing impurity concentration
Solution Approach 1:
The contact structure is segmented into two distinct metallic films: a first metallic film (high work function material such as Pt, Ir, or Ru) and a second metallic film (low work function material such as Ti, Mo, or W). Each layer serves a specific function - the first metallic film forms a Schottky junction with the second semiconductor layer to prevent leakage, while the second metallic film forms an ohmic junction with the third semiconductor layer to enable low-resistance contact, thereby resolving the contact resistance issue without requiring increased impurity concentration
Solution Approach 2:
The patent employs a composite metallic film structure combining materials with different work functions. The first metallic film uses high work function materials (Pt, Ir, Ru) to create a Schottky barrier, while the second metallic film uses low work function materials (Ti, Mo, W) to create an ohmic contact. This composite approach allows simultaneous achievement of high barrier height and low contact resistance, solving the technical contradiction without increasing device complexity in terms of fabrication steps
2Reliability
If local ion implantation is used to increase n-type impurity concentration for reducing contact resistance, then contact resistance decreases, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The invention extracts and eliminates the local ion implantation step from the manufacturing process. Instead of using ion implantation to increase n-type impurity concentration in the contact region, the patent achieves low contact resistance through the dual-metallic film structure alone, where the second metallic film (low work function) naturally forms an ohmic junction with the third semiconductor layer, thereby improving productivity by removing a complex and time-consuming process step
Solution Approach 2:
The first metallic film acts as an intermediary layer between the second semiconductor layer and the second metallic film. It forms a Schottky junction with the second semiconductor layer to prevent leakage currents, while allowing the second metallic film to form an ohmic junction with the third semiconductor layer. This intermediary structure achieves the desired electrical characteristics without requiring additional impurity concentration adjustments through ion implantation
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 decreases contact resistance by forming specific junctions, eliminating the need for local ion implantation processes and enhancing the device's performance.
Implementation Method 1
a first metallic film in contact with the second semiconductor layer in the first trench, wherein the first metallic film includes a high work function metal
Implementation Method 2
a second metallic film in contact with the third semiconductor layer and the first metallic film in the first trench, wherein the second metallic film includes a low work function metal having a lower work function than that of the first metallic film
Data Source
AI summary
A semiconductor device according to one embodiment includes a semiconductor part including a first semiconductor layer, a second semiconductor layer located on the first semiconductor layer, and a third semiconductor layer located in a first trench of the second semiconductor layer, a first electrode located on a back surface of the first semiconductor layer, a first metallic film in contact with the second semiconductor layer in the first trench, a second metallic film in contact with the third semiconductor layer and the first metallic film in the first trench, and a second electrode in contact with the second metallic film in the first trench. The first metallic film includes a high work function metal, and the second metallic film includes a low work function metal having a lower work function than that of the first metallic film.