Self-Aligned Thinning of Semiconductor Substrates via PN-Junction Detection
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Solution Overview
Problem
The accuracy of semiconductor substrate thinning is critical for high-voltage semiconductor devices like IGBTs, where variations in substrate thickness can affect reproducible electrical performance and robustness against short-circuit current.
Innovation Solution
A method involving the incorporation of first and second dopant atoms of different conductivity types to form a pn-junction near the interface between the semiconductor substrate and an epitaxial layer, allowing for self-aligned thinning that stops at the pn-junction or depletion zone, ensuring precise control and stability during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thinning processes are used for semiconductor substrates, then manufacturing simplicity is maintained, but thinning accuracy and thickness control deteriorate
Solution Approach 1:
A pn-junction is formed in advance within the semiconductor substrate before the thinning process. This pre-formed junction serves as a reference structure that enables self-aligned thinning, where the etching process automatically stops at the desired thickness when reaching the pn-junction. The preliminary formation of this electrical structure provides a built-in thickness reference that improves thinning accuracy without requiring complex external measurement and control systems.
Solution Approach 2:
The pn-junction structure serves as a self-aligned reference that automatically controls the thinning process. During etching, the process naturally stops when the pn-junction is reached, as indicated by changes in etch rate or electrical properties. This self-service mechanism eliminates the need for complex real-time thickness monitoring and control systems, achieving high precision while maintaining relative process simplicity.
2Reliability
If substrate thickness varies, then manufacturing ease is maintained, but electrical performance reproducibility deteriorates
Solution Approach 1:
The patent replaces mechanical thickness measurement and control systems with an electrical reference system based on the pn-junction. Instead of relying on mechanical gauges or complex sensor systems to control substrate thickness, the invention uses the electrical properties of the pre-formed pn-junction as a reference. The thinning process is controlled by electrical signals detected when the etching front reaches the pn-junction, providing more precise and reproducible thickness control that directly impacts electrical performance.
Solution Approach 2:
The invention changes the control parameter from mechanical thickness measurement to electrical property detection. By monitoring electrical characteristics (such as current or voltage changes) that occur when the etching process reaches the pn-junction, the system achieves more precise and reproducible thickness control. This parameter change enables better correlation between substrate thickness and electrical performance, improving overall device reliability.
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 improves the accuracy and reliability of semiconductor device thinning, enhancing the reproducibility of electrical performance by maintaining a consistent pn-junction position throughout the manufacturing process.
Implementation Method 1
incorporating first dopant atoms of a first conductivity type into a semiconductor substrate to form a first doping region comprising the first conductivity type
Implementation Method 2
a pn-junction is located between the first doping region and the second doping region. The self-aligned thinning process is self-controlled based on the location of the pn-junction
Data Source
AI summary
A method for forming a semiconductor device includes incorporating first dopant atoms of a first conductivity type into a semiconductor substrate to form a first doping region of the first conductivity type. Further, the method includes forming an epitaxial semiconductor layer on the semiconductor substrate and incorporating second dopant atoms of a second conductivity type before or after forming the epitaxial semiconductor layer to form a second doping region including the second conductivity type adjacent to the first doping region so that a pn-junction is located between the first doping region and the second doping region. The pn-junction is located in a vertical distance of less than 5 μm to an interface between the semiconductor substrate and the epitaxial semiconductor layer. Additionally, the method includes thinning the semiconductor substrate based on a self-aligned thinning process. The self-aligned thinning process is self-controlled based on the location of the pn-junction.