SiC Bipolar Device Resistor Layer for Parallel Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bipolar devices with silicon carbide semiconductor layers face issues with current concentration due to variations in doping concentration and film thickness, leading to unstable operation when connected in parallel, as the resistance value of the positive temperature coefficient resistor cannot be consistently achieved.
Innovation Solution
A semiconductor device with a silicon carbide drift layer and a second silicon carbide layer of a different conductivity type, where the second layer is formed after the drift layer, allowing for adjustment of its impurity concentration and film thickness to achieve a desired positive temperature coefficient of resistance, thereby preventing current concentration and ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an n-type substrate layer doped at low concentration is used as a resistor with positive temperature coefficient, then current concentration is alleviated, but variation in doping concentration or film thickness causes variation in resistance value, making it ineffective in some cases
Solution Approach 1:
The patent changes the formation method of the resistor layer from epitaxial growth to ion implantation. This allows precise control of the resistance value by adjusting ion implantation conditions (dose, energy, distribution) rather than relying on epitaxial parameters (doping concentration, film thickness) which have high variation. The ion implantation method enables independent optimization of resistance value without affecting other device parameters.
Solution Approach 2:
The patent replaces the epitaxial growth process with ion implantation to form the resistor layer. This substitution allows for more precise and controllable resistance value formation, as ion implantation parameters can be independently adjusted to achieve desired resistance characteristics without the variability inherent in epitaxial doping processes.
2Ease of manufacture
If the drift layer is formed after film formation for the n-type semiconductor layer, then the device structure is completed, but a resistor with suitable resistance value cannot be formed because the drift layer variation cannot be compensated
Solution Approach 1:
The patent performs ion implantation to form the resistor layer after the drift layer is already formed. This preliminary action allows the resistance value to be adjusted based on the actual drift layer characteristics without requiring re-epitaxial growth. The ion implantation process can be precisely controlled to compensate for any variations in the drift layer, achieving the desired resistance value even after the main device structure is completed.
3Power
If many bipolar devices are connected in parallel with negative temperature coefficient, then high current capacity is achieved, but current concentrates on devices with greater voltage drop, leading to breakdown
Solution Approach 1:
The patent changes the temperature coefficient of the device from negative to positive by adding a resistor layer with positive temperature coefficient in series. This parameter change fundamentally alters the thermal behavior: as temperature increases, the resistance increases, which automatically limits current and prevents thermal runaway. This allows parallel-connected devices to operate stably with improved current distribution and reliability while maintaining high current capacity.
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 configuration effectively adjusts the resistance value and temperature coefficient of the second silicon carbide layer, ensuring stable operation of bipolar devices even when multiple devices are connected in parallel by preventing current concentration and maintaining high film quality.
Implementation Method 1
the second silicon carbide layer has a positive temperature coefficient of resistance
Data Source
AI summary
The present techniques relate to a semiconductor device having resistance which has a positive temperature coefficient and a suitable value, and to a method for manufacturing a semiconductor device having resistance which has a positive temperature coefficient and a suitable value. The semiconductor device related to the present techniques is a bipolar device in which a current flows through a pn junction. The semiconductor device includes an n-type silicon carbide drift layer, a p-type first silicon carbide layer formed on the silicon carbide drift layer, and a p-type second silicon carbide layer formed on the first silicon carbide layer. Then, the second silicon carbide layer has a positive temperature coefficient of resistance.