Semiconductor Pad Insulation Structure for Nickel Plating Crack Prevention
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Solution Overview
Problem
Semiconductor devices face reliability issues due to cracks in the insulation film caused by stress from nickel plating films during the wire bonding process, which can lead to moisture absorption and oxidation of the pad's surface, affecting the device's performance and longevity.
Innovation Solution
A semiconductor device structure is developed with a silicon oxide insulation film (PA1) covered by a silicon nitride or silicon oxynitride film (PA2), where the nickel plating film thickness and the distance from the pad's outer circumference to the inner wall of the opening are optimized to prevent crack formation, using a specific formula to ensure the reliability of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a nickel plating film is formed on the pad to improve wire bonding reliability, then bonding strength is improved, but stress from the plating film causes cracks in the insulation film
Solution Approach 1:
The insulation film is divided into multiple layers (first insulation film made of silicon oxide, second insulation film made of silicon nitride or silicon oxynitride) with different mechanical properties. The first layer provides stress absorption while the second layer provides protection, segmenting the stress management function across layers.
Solution Approach 2:
The patent optimizes specific parameters including the thickness of the nickel plating film (T1), the distance from pad outer circumference to opening inner wall (L1), and the relationship L1 > T1 × 2.45 - 4.61. These parameter changes balance the stress between the plating film and insulation film to prevent cracking while maintaining bonding strength.
2Stress or pressure
If the nickel plating film thickness is increased to reduce stress, then stress transmission is reduced, but the distance from pad to opening must be increased
Solution Approach 1:
The patent establishes a quantitative relationship between plating film thickness (T1) and opening distance (L1) through the formula L1 > T1 × 2.45 - 4.61. This parameter optimization allows minimal opening distances while preventing cracks, balancing stress reduction with compact device design.
Solution Approach 2:
The patent uses a composite insulation film structure combining silicon oxide and silicon nitride/silicon oxynitride layers. This composite structure provides different mechanical properties in each layer, allowing stress management with optimized geometry and reduced opening distances.
3Object-affected harmful factors
If cracks form in the insulation film due to stress, then moisture absorption increases, but the pad surface becomes oxidized
Solution Approach 1:
The dual-layer insulation film structure segments the protective function: the first silicon oxide layer provides moisture barrier properties while the second silicon nitride/silicon oxynitride layer provides oxidation resistance and mechanical strength, protecting the pad from both moisture and oxidation.
Solution Approach 2:
The insulation film layers act as intermediary protective barriers between the nickel plating film/stress source and the pad surface. By preventing crack formation through optimized stress distribution, these intermediary layers block moisture and oxygen pathways to the pad surface.
Data Source
AI summary
A pad is formed on an interlayer insulation film, a first insulation film is formed on the interlayer insulation film so as to cover the pad, and a second insulation film is formed on the first insulation film so as to cover the pad. The first insulation film includes a first opening partially exposing the pad, and the second insulation film includes a second opening partially exposing the pad, and the second opening is included in the first opening in plan view. The first insulation film is made of silicon oxide, and the second insulation film is made of silicon nitride or silicon oxynitride. A nickel plating film is formed on the pad exposed from the second opening. A distance from an outer circumference of the pad to an inner wall of the first opening increases in accordance with a thickness of the nickel plating film.