Semiconductor Pad Electrode Mounting Portion for Rewiring Adhesion
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Solution Overview
Problem
The reliability of semiconductor devices with rewiring deteriorates due to peeling off of the rewiring from the surface protection film during the miniaturization of semiconductor chips, primarily caused by adhesion strength deterioration between the rewiring and the surface protection film, especially at the pad electrode's end portion under tensile stress during the wire bonding process.
Innovation Solution
The semiconductor device incorporates a pad electrode with a rectangular shape and a pad electrode mounting portion, both larger than the pad electrode, to reduce the pressing force per unit area and enhance adhesion, using an inorganic insulating film as the surface protection film to prevent peeling and improve connection reliability, with a copper plating film and nickel plating film for low resistance and oxidation prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the semiconductor chip size is miniaturized, then the productivity and integration density are improved, but the adhesion strength between the rewiring and surface protection film deteriorates causing wire peeling
Solution Approach 1:
The pad electrode mounting portion is designed to be larger than the pad electrode itself before wire bonding occurs. This preliminary design ensures that the pressing force during wire bonding is distributed over a larger area, preventing adhesion deterioration and wire peeling even as chip size is miniaturized.
Solution Approach 2:
The patent applies different sizes to different portions of the pad structure: the pad electrode mounting portion is made larger than the pad electrode. This local quality differentiation concentrates the stress distribution benefit exactly where needed (at the bonding interface) without increasing the overall chip size.
2Reliability
If the pad opening size is increased to improve adhesion, then the wire bonding reliability is improved, but the chip area is increased preventing miniaturization
Solution Approach 1:
The patent creates a localized larger area only at the pad electrode mounting portion, which is a small fraction of the total chip area. This allows improved adhesion and wire bonding reliability without significantly increasing the overall chip area, thus enabling miniaturization.
Solution Approach 2:
Instead of increasing the pad opening size in the planar dimension (which would increase chip area), the patent extends the pad electrode mounting portion in the vertical dimension (as a mounting structure), thereby improving adhesion without occupying more chip area.
3Strength
If the pressing force during wire bonding is increased to improve adhesion, then the wire bonding strength is improved, but the stress on the surface protection film increases causing rewiring peeling
Solution Approach 1:
The pad electrode mounting portion is pre-designed to be larger than the pad electrode to anticipate and distribute the pressing force that will be applied during wire bonding. This preliminary design prevents stress concentration and subsequent rewiring peeling while still achieving strong wire bonding.
Solution Approach 2:
The larger pad electrode mounting portion acts as a cushioning structure before wire bonding occurs. It absorbs and distributes the pressing force stress, preventing it from concentrating on the surface protection film and causing rewiring peeling, while still providing sufficient bonding strength.
Data Source
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AI summary
The semiconductor device includes a plurality of wiring layers formed on a semiconductor substrate, a pad (9a) formed on an uppermost wiring layer (9) of the plurality of wiring layers (5,7,9), a surface protection film (10) which includes an opening (10a) on the pad (9a) and is made of an inorganic insulating film, a rewiring (12) formed on the surface protection film (10); a pad electrode (13) formed on the rewiring, and a wire (20) connected to the pad electrode (13). The rewiring (12) includes a pad electrode mounting portion (121) on which the pad electrode (13) is mounted, a connection portion which is connected to the pad (9a), and an extended wiring portion which couples the pad electrode mounting portion (121) and the connection portion, and the pad electrode mounting portion (121) has a rectangular shape when seen in a plan view.