SiC Schottky Diode Forward Characteristic Stabilization
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Solution Overview
Problem
Conventional methods for manufacturing silicon carbide Schottky barrier diodes face challenges in stabilizing forward characteristics, particularly barrier heights φB, due to variations in processing conditions and the inability to form stable Ti Schottky junctions at high temperatures, which limits reproducibility and suitability for mass production.
Innovation Solution
The method involves forming a protective film on the silicon carbide substrate, followed by heat treatment to create an ohmic junction, and then applying Ti sintering at a lower temperature (400° C. to 600° C.) after forming the Schottky metal film to stabilize the Schottky junction, reducing variations in forward characteristics and barrier heights φB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Ni ohmic junction is formed on the rear surface first and then the Ti Schottky junction is formed on the front surface, then the ohmic junction can be properly formed by annealing at high temperature, but the Ti Schottky junction cannot be kept in an appropriate state at such high temperature and forward characteristics are not stabilized
Solution Approach 1:
The patent divides the annealing process into two separate stages: first annealing the Ni ohmic junction at high temperature (1000°C) to form the rear surface contact, then annealing the Ti Schottky junction at lower temperature (400-600°C) to form the front surface contact. This segmentation allows each junction to be optimized at its appropriate temperature without compromising the other, resolving the contradiction between forming a reliable ohmic junction and maintaining Schottky junction stability.
Solution Approach 2:
The patent performs preliminary formation of the Ni ohmic junction on the rear surface before forming the Ti Schottky junction on the front surface. By completing the high-temperature annealing for the ohmic junction first, the substrate is then prepared for the lower-temperature Schottky junction formation, ensuring that the Schottky metal is not exposed to temperatures that would degrade its characteristics.
2Manufacturing precision
If metals of the same type are used as Schottky material for front surface and ohmic material for rear surface, then excellent junctions can be obtained by annealing at one time, but process margins are remarkably narrowed and manufacturing stability is reduced
Solution Approach 1:
The patent applies different metal materials to different surfaces of the semiconductor device: Ti is used for the Schottky junction on the front surface where specific electrical characteristics are required, while Ni is used for the ohmic junction on the rear surface where low contact resistance is prioritized. This local differentiation allows each junction to be optimized for its specific function, maintaining excellent quality while providing sufficient process margins for manufacturability.
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 results in silicon carbide semiconductor devices with consistent forward characteristics and reduced variations in barrier heights φB, enhancing the reproducibility and stability of the manufacturing process.
Implementation Method 1
heat treatment to the silicon carbide substrate at a predetermined temperature so as to form an ohmic junction
Implementation Method 2
applying heat treatment to the silicon carbide substrate at a predetermined temperature
Implementation Method 3
applying heat treatment to the silicon carbide substrate at a temperature from 400° C. to 600° C. so as to form a Schottky junction of desired characteristics
Implementation Method 4
applying heat treatment to the silicon carbide substrate at a temperature from 400° C. to 600° C.
Data Source
AI summary
An object of the invention is to provide a method for manufacturing a silicon carbide semiconductor device having constant characteristics with reduced variations in forward characteristics. The method for manufacturing the silicon carbide semiconductor device according to the invention includes the steps of: (a) preparing a silicon carbide substrate; (b) forming an epitaxial layer on a first main surface of the silicon carbide substrate; (c) forming a protective film on the epitaxial layer; (d) forming a first metal layer on a second main surface of the silicon carbide substrate; (e) applying heat treatment to the silicon carbide substrate at a predetermined temperature to form an ohmic junction between the first metal layer and the second main surface of the silicon carbide substrate; (f) removing the protective film; (g) forming a second metal layer on the epitaxial layer; and (h) applying heat treatment to the silicon carbide substrate at a temperature from 400° C. to 600° C. to form a Schottky junction of desired characteristics between the second metal layer and the epitaxial layer.