SiC Device Altered Layer Removal via Segmented Etching
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Solution Overview
Problem
The existing methods for removing the altered layer formed during activation annealing in silicon carbide Schottky diode manufacturing often result in surface irregularities, increased leakage current, and prolonged processing times, especially when using sacrificial oxidation or plasma treatment.
Innovation Solution
A method involving ion implantation, activation annealing, dry etching to remove a surface layer, forming a sacrificial oxide film, and subsequent wet etching to remove the altered layer, which shortens processing time and reduces surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sacrificial oxidation is performed to remove the altered layer, then the altered layer can be removed, but surface irregularities are enhanced and leakage current increases
Solution Approach 1:
The removal of the altered layer is divided into multiple steps: first removing a portion by etching, then performing sacrificial oxidation, and finally removing the sacrificial oxide film. This segmented approach prevents surface irregularities from being enhanced while still effectively removing the altered layer, thereby reducing leakage current.
Solution Approach 2:
A portion of the altered layer is removed by etching before performing sacrificial oxidation. This preliminary action reduces the thickness of the altered layer, preventing excessive surface irregularities during the subsequent sacrificial oxidation step, thus maintaining surface flatness and reducing leakage current.
2Manufacturing precision
If the thickness of the sacrificial oxide film is increased to match the altered layer thickness, then complete removal is achieved, but processing time increases significantly
Solution Approach 1:
The altered layer removal is segmented into two parts: a first portion removed by etching and a second portion removed via sacrificial oxidation. This segmentation allows the sacrificial oxide film to be thinner, reducing the time required for both formation and removal of the sacrificial oxide film while ensuring complete altered layer removal.
Solution Approach 2:
The process maintains continuous progress toward altered layer removal by combining etching and sacrificial oxidation. The etching step pre-reduces the altered layer thickness, enabling the subsequent sacrificial oxidation to complete the removal efficiently without requiring excessive time.
3Loss of time
If plasma treatment is used to remove the altered layer, then processing time is reduced, but new damage is caused to the SiC surface
Solution Approach 1:
A sacrificial oxide film is introduced as an intermediary layer between the SiC surface and the final removal step. The oxide film is formed by sacrificial oxidation and then removed by wet etching, providing a gentler removal mechanism that avoids the surface damage caused by direct plasma treatment while still achieving altered layer removal efficiently.
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 method effectively inhibits the generation of surface irregularities and reduces leakage current, allowing for efficient removal of the altered layer without increasing processing time, thereby enhancing the manufacturing of silicon carbide semiconductor devices.
Implementation Method 1
a method, in which ions of a p-type impurity such as Al (aluminum) or B (boron) are implanted in an n-type epitaxial layer
Implementation Method 2
activation annealing is performed to the layer through a high-temperature heat treatment at about 1,500° C. or higher
Implementation Method 3
activation annealing is performed to the layer through a high-temperature heat treatment
Implementation Method 4
the surface of the SiC is subsequently cleaned by etching with plasma of a hydrogen/oxygen mixture gas or plasma of a gas containing fluorine atoms
Implementation Method 5
sacrificial oxidation is performed to a surface layer of the SiC after the activation annealing to form a sacrificial oxide film
Implementation Method 6
the altered layer is removed together with the sacrificial oxide film
Data Source
AI summary
An object is to provide a method for manufacturing a silicon carbide semiconductor device in which a time required for removing a sacrificial oxide film can be shortened and damage to a surface of the silicon carbide layer can be reduced. The method for manufacturing a silicon carbide semiconductor device includes: (a) performing ion implantation to a silicon carbide layer; (b) performing activation annealing to the ion-implanted silicon carbide layer 2; (c) removing a surface layer of the silicon carbide layer 2, to which the activation annealing has been performed, by dry etching; (d) forming a sacrificial oxide film on a surface layer of the silicon carbide layer, to which the dry etching has been performed, by performing sacrificial oxidation thereto; and (e) removing the sacrificial oxide film by wet etching.