Semiconductor Bump Electrode Void Prevention via Solder Reflow
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Solution Overview
Problem
Conventional methods for forming bump electrodes on semiconductor substrates often result in voids due to trapped gas between the solder layer and the opening, leading to cracking and corrosion issues during heat treatment and usage, necessitating additional processes like defoaming treatments to prevent these voids.
Innovation Solution
A method where a semiconductor substrate is processed to form a first and second wiring with insulation films, an opening is created with a sloping shape, and a solder layer is applied to extend beyond the opening's end, allowing the solder to flow into the opening during reflow, thereby filling it and preventing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solder layer is formed thick on the back surface to cover the opening, then the opening is covered and wiring is protected, but gas trapped between the solder paste and opening forms voids after reflowing
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on the back surface before applying the solder layer. This protrusion serves as a pre-prepared structure that guides the solder flow during reflow, ensuring the solder naturally fills the opening without trapping gas. The protrusion is formed in advance through photolithography and etching processes, creating a physical guide structure that prevents void formation before the soldering process occurs.
Solution Approach 2:
The protrusion acts as an intermediary structure between the opening and the solder layer. It mediates the solder flow by providing a stepped surface that allows solder to gradually fill the opening from the back surface, preventing gas entrapment. The protrusion translates the solder application process into a controlled filling operation that eliminates voids while maintaining electrical connection reliability.
2Manufacturing precision
If a defoaming treatment is performed while forming the solder layer, then void formation is prevented, but the manufacturing process becomes more complex with additional steps
Solution Approach 1:
The patent applies self-service by designing a structure (protrusion) that automatically prevents void formation during the soldering process itself, without requiring separate defoaming treatments. The protrusion's geometry naturally guides solder flow to fill the opening completely, making the soldering process self-correcting and eliminating the need for additional defoaming process steps.
3Reliability
If the bump electrode is formed away from the opening, then void formation is prevented, but the electrode cannot properly connect to the wiring through the opening
Solution Approach 1:
The patent applies segmentation by dividing the back surface structure into multiple levels: the base surface, the protrusion structure, and the opening. This segmentation creates distinct functional zones where the protrusion serves as an intermediate structure that both covers the opening and provides a surface for the bump electrode, allowing the electrode to form directly over the opening without voids while maintaining electrical connection.
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 ensures a void-free bump electrode formation without additional processes, enhancing reliability and preventing cracking and corrosion by ensuring the solder fills the opening, thus maintaining electrode integrity.
Implementation Method 1
reflowing the solder layer so that a portion of the solder layer flows into the opening
Data Source
AI summary
When a bump electrode is formed on an opening formed in a semiconductor substrate, the invention prevents a void that is caused by gas trapped in the opening. A method of manufacturing a semiconductor device of the invention includes forming a first wiring on a main surface of a semiconductor substrate, forming an opening in the semiconductor substrate from the back surface to the main surface so as to expose the back surface of the first wiring, forming a second wiring connected to the back surface of the first wiring and extending from inside the opening onto the back surface of the semiconductor substrate, forming a solder layer connected to part of the second wiring on the bottom of the opening and extending from inside the opening onto the back surface of the semiconductor substrate, and forming a bump electrode on the opening by reflowing the solder layer.