SiC Epitaxial Wafer Carbon-Rich Surface Control for Gate Oxide Reliability
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Solution Overview
Problem
SiC wafers exhibit significant variations in device characteristics due to unevenness on the surface, leading to defective chips and reduced yield, particularly in power devices, which is attributed to the composition of the wafer surface affecting the reliability of the gate insulating film.
Innovation Solution
A SiC wafer with an epitaxial layer having a controlled composition ratio of C—Si at 50 atm% or less, achieved through a carbon-rich treatment, which stabilizes the surface composition to reduce variations in the lifetime of the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth is performed without carbon-rich treatment, then the epitaxial layer can be formed, but the surface composition becomes uneven leading to significant variations in device characteristics and reduced yield
Solution Approach 1:
The patent applies parameter changes by controlling the carbon supply ratio during epitaxial growth to create a carbon-rich state at the wafer surface. Specifically, the carbon supply ratio is set to 30-70 at%, which transforms the surface composition to achieve a carbon-rich state. This parameter control ensures uniform surface composition across the wafer, reducing variations in device characteristics and improving both manufacturing precision and reliability of the gate insulating film.
2Ease of manufacture
If the wafer surface composition is not controlled, then the manufacturing process is simpler, but significant variations in device characteristics occur leading to defective chips
Solution Approach 1:
The patent introduces control of the carbon supply ratio parameter during epitaxial growth to achieve a carbon-rich state. By setting the carbon supply ratio to 30-70 at%, the process ensures uniform surface composition that prevents device characteristic variations. This parameter control, while adding a specification requirement, actually simplifies the overall manufacturing by preventing defects and improving yield, thus resolving the contradiction between ease of manufacture and productivity.
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 carbon-rich treatment enhances the reliability of SiC wafers by extending the time before dielectric breakdown occurs and uniformizing the characteristics of the gate insulating film, thereby improving yield and reducing defective chips.
Implementation Method 1
an epitaxial layer formed on the SiC substrate and containing SiC
Data Source
AI summary
A SiC wafer including a SiC substrate and an epitaxial layer formed on the SiC substrate and containing SiC is provided, and a composition ratio of C—Si of an upper surface of the epitaxial layer is 50 atm % or less.