Reverse Blocking IGBT Separation Layer Formation
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Solution Overview
Problem
The existing methods for manufacturing reverse blocking IGBTs face challenges such as long lead times due to trench formation and the occurrence of crystal defects during thermal diffusion processes, which reduce yield and lead to reverse breakdown voltage defects.
Innovation Solution
A method involving heat treatment in an inert gas atmosphere at high temperatures for extended periods, specifically between 1290°C and 1350°C, is employed to form a semiconductor device without crystal defects, using silicon wafers manufactured by the Czochralski or floating zone methods, ensuring the formation of a separation layer without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal diffusion process is performed at high temperature for long time to form separation layer, then separation layer formation is achieved, but crystal defects occur in silicon wafer reducing yield
Solution Approach 1:
The patent applies inert gas atmosphere (nitrogen or argon) during high-temperature heat treatment to prevent oxidation and chemical reactions that cause crystal defects. By creating an inert environment, the silicon wafer is protected from harmful interactions with oxygen and other reactive gases, allowing long-duration thermal diffusion without generating defects that would reduce yield.
Solution Approach 2:
The patent optimizes heat treatment parameters including temperature range (1290°C to 1350°C), duration (10 to 100 hours), and atmosphere composition to achieve separation layer formation while minimizing crystal defects. By carefully controlling these parameters, the process balances the need for thorough diffusion with the prevention of defect formation.
2Manufacturing precision
If trench formation is performed to create separation layer, then separation structure is achieved, but lead time increases
Solution Approach 1:
The patent extracts the separation layer formation process from the complex trench formation methodology. Instead of forming deep trenches and performing multiple etching steps, the invention directly forms the separation layer through thermal diffusion in an inert atmosphere, eliminating unnecessary process steps and significantly reducing lead time while maintaining the required separation structure.
Solution Approach 2:
The patent replaces mechanical/chemical etching processes with thermal diffusion in an inert atmosphere. This substitution transforms the separation layer formation from a multi-step mechanical removal process into a single thermal treatment process, dramatically simplifying the manufacturing flow and reducing production time.
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 enhances the yield of semiconductor devices by preventing crystal defects and reducing the time required for separation layer formation, thereby improving the reliability and efficiency of reverse blocking IGBTs.
Implementation Method 1
a heat treatment in an inert gas atmosphere at a temperature equal to or more than 1290° C. and less than a melting point of silicon is performed for a silicon wafer
Implementation Method 2
performing a heat treatment in an inert gas atmosphere at a temperature equal to or more than 1290° C. and less than a melting point of silicon
Data Source
AI summary
A reverse blocking IGBT is manufactured using a silicon wafer sliced from a single crystal silicon ingot which is manufactured by a floating method using a single crystal silicon ingot manufactured by a Czochralski method as a raw material. A separation layer for ensuring a reverse blocking performance of the reverse blocking IGBT is formed by diffusing impurities implanted into the silicon wafer using a thermal diffusion process. The thermal diffusion process for forming the separation layer is performed in an inert gas atmosphere at a temperature equal to or more than 1290° C. and less than the melting point of silicon. In this way, no crystal defect occurs in the silicon wafer and it is possible to prevent the occurrence of a reverse breakdown voltage defect or a forward defect in the reverse blocking IGBT and thus improve the yield of a semiconductor element.