Soft Switching Semiconductor Device Broad Buffer Structure
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Solution Overview
Problem
Current methods for forming a broad buffer structure in semiconductor devices, such as diodes and IGBTs, face challenges in achieving high donor concentration profiles deep within the bulk material, particularly with ion implantation of phosphorus and arsenic, which results in low efficiency and high manufacturing costs due to difficulties in controlling concentration profiles and the risk of wafer breakage during processing.
Innovation Solution
A manufacturing method involving the introduction of oxygen into the semiconductor substrate, followed by charged particle irradiation and heat treatment, to create complex donors comprising oxygen and hydrogen atoms, which form a broad buffer structure with improved controllability and yield, using FZ bulk wafers to achieve fast operation and low losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion implantation of phosphorus and arsenic is used to form a broad buffer structure, then high donor concentration can be achieved, but manufacturing cost increases and wafer breakage risk occurs
Solution Approach 1:
Oxygen atoms serve as an intermediary substance that converts to electron donors through heat treatment after charged particle irradiation. Instead of directly implanting phosphorus or arsenic, the patent uses oxygen as a mediator that transforms into the desired donor atoms under thermal processing, thereby avoiding the complications of direct ion implantation while achieving the same electrical effect
Solution Approach 2:
The patent replaces the mechanical ion implantation process with a combination of charged particle irradiation followed by thermal conversion. Instead of mechanically forcing phosphorus or arsenic ions into the wafer (which causes damage and high costs), the system uses charged particle irradiation to create conditions for oxygen conversion, followed by heat treatment to generate the desired donor concentration profile
2Quantity of substance
If conventional ion implantation methods are used, then donor concentration can be increased, but control of concentration profile becomes difficult
Solution Approach 1:
The patent changes the fundamental parameter from direct donor atom implantation to oxygen atom conversion through heat treatment. By controlling the heat treatment temperature and duration, the concentration profile can be precisely adjusted as oxygen atoms convert to electron donors at controlled rates, providing superior profile control compared to ion implantation
Solution Approach 2:
The patent performs preliminary charged particle irradiation to create specific conditions in the semiconductor lattice before heat treatment. This preliminary action prepares the structure for controlled oxygen conversion, ensuring that the subsequent thermal process produces the desired concentration profile with high precision
3Speed
If high speed operation is achieved, then power conversion efficiency improves, but reverse recovery losses increase
Solution Approach 1:
The patent creates a broad buffer structure with spatially varying donor concentration, where the concentration peaks at a specific depth and decreases toward the surface. This local quality variation in the buffer region enables high-speed operation while controlling reverse recovery characteristics, as the gradual concentration change reduces abrupt carrier termination
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 method enables the formation of semiconductor devices with soft switching characteristics and reduced reverse recovery losses, achieving efficient and cost-effective manufacturing with high controllability and yield, while preventing wafer breakage and maintaining low electrical losses.
Implementation Method 1
the location of the maximum impurity concentration comprises oxygen atoms and atoms lighter than oxygen
Implementation Method 2
performing heat treatment, to convert protons into donors in the vicinity of the proton range Rp within the bulk material
Implementation Method 3
irradiating a FZ (Float Zone) bulk wafer with protons (H+) and performing heat treatment, to convert protons into donors
Implementation Method 4
A diode with a broad buffer structure can realize soft recovery characteristics and oscillation suppression in high-speed operation
Data Source
AI summary
After introducing oxygen into an N− type FZ wafer serving as an N− type first semiconductor layer, a P type second semiconductor layer and an anode are formed on a surface of the FZ wafer. The FZ wafer is irradiated with protons from the side of the anode, introducing crystal defects into the FZ wafer. By performing heat treatment to recover the crystal defects in the FZ wafer, the net doping concentration of a portion within the first semiconductor layer is made higher than the initial net doping concentration of the FZ wafer, and a desired broad buffer structure is formed. Accordingly, a semiconductor device with fast operation and low losses, and having soft switching characteristics, can be manufactured inexpensively using FZ bulk wafers, with good controllability and yields.