Polysilicon Buffer Layer for SiC MOSFET Wire Bonding
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Solution Overview
Problem
The existing semiconductor devices face challenges in achieving a smooth surface for wire connection due to uneven semiconductor layers, leading to poor wire adhesion and increased assembly costs and reliability issues.
Innovation Solution
A polysilicon layer is used as an unevenness buffer to create a smoother surface for the electrode, allowing for improved wire connection and adhesion by backfilling recesses and forming ohmic junctions with low contact resistance without the need for additional treatments like RTA or flattening processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal material is directly deposited on the uneven topmost surface of the semiconductor layer, then the manufacturing process is simple, but the surface of the surface electrode becomes uneven causing poor wire adhesion
Solution Approach 1:
An unevenness buffer layer is introduced as an intermediary between the uneven semiconductor layer and the metal material. This buffer layer has a smoother top surface than the semiconductor layer, providing a flat foundation for metal deposition and wire bonding, thereby improving wire adhesion without requiring complex additional processing steps.
2Reliability
If the uneven shape is backfilled to create a flat surface, then wire connection area is expanded and adhesion is improved, but additional manufacturing steps are required
Solution Approach 1:
The unevenness buffer layer is designed to automatically backfill the uneven shapes of the semiconductor layer through its material properties and deposition process. The layer self-adjusts to create a smooth surface without requiring separate flattening or planarization steps, thereby improving wire connection reliability while maintaining manufacturing efficiency.
3Manufacturing precision
If polysilicon layer is deposited to backfill recesses, then the surface becomes smoother for better wire adhesion, but the manufacturing process time increases
Solution Approach 1:
The deposition parameters of the polysilicon layer are optimized to achieve adequate backfilling of recesses within a controlled thickness range. By adjusting deposition conditions and controlling the layer thickness to be 2/3 or more of the maximum recess width, the patent achieves sufficient surface flatness for wire bonding while minimizing additional process 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
The polysilicon layer enhances wire adhesion, reduces wire stripping frequency, and simplifies the manufacturing process by providing a flat surface for electrodes, thereby improving the reliability and yield of semiconductor device assembly.
Implementation Method 1
it is possible to easily backfill a recess of the uneven shape. Thus, it is possible to make the surface of the surface electrode smooth or flat with an easy method, that is, depositing the polysilicon.
Implementation Method 2
A first conductive-type polysilicon is a substance capable of contacting a first conductive-type SiC with a low contact resistance. Therefore, it is possible to easily form an ohmic junction between the SiC layer (first conductive-type impurity region) and the polysilicon layer (first conductive-type portion)
Data Source
AI summary
[Problem] To provide a semiconductor device in which the surface of a metal electrode arranged on the outermost surface can be made flat or smooth, and a method for producing said semiconductor device.[Solution] This semiconductor device (1) comprises: an SiC epitaxial layer (3) that has an uneven shape formed, on the basis of a height difference (H1), on the outermost surface where a semiconductor element (MOSFET) is arranged; and a source electrode (13) made of a metal material and formed on the SiC epitaxial layer (3). A polysilicon layer (12) having a surface (121) that is smoother than said uneven shape is provided between the surface (31) of the SiC epitaxial layer (3) and the source electrode (13).