Alternating Stress Passivation Film for Semiconductor Wafer Warping
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Solution Overview
Problem
Semiconductor wafers often warp and passivation films crack due to residual compressive stress from differences in thermal expansion coefficients of materials, which existing passivation films exacerbate by generating additional compressive stress.
Innovation Solution
A passivation film is formed by alternately stacking a first insulation film with larger tensile stress and a second insulation film with smaller tensile stress, generating overall tensile stress to alleviate compressive stress and prevent warping and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation film generating compressive stress is formed on a wafer surface with residual compressive stress, then the passivation film provides protective coverage, but the wafer warps and the passivation film cracks due to accumulated compressive stresses
Solution Approach 1:
Instead of using a passivation film that generates compressive stress as in conventional technology, the present invention uses a passivation film that generates tensile stress. This inversion of the stress type allows the passivation film to counteract the residual compressive stress in the wafer, preventing warping and cracking while maintaining protective coverage
Solution Approach 2:
The invention changes the stress parameter of the passivation film from compressive to tensile. By controlling the film composition and deposition conditions, the passivation film generates tensile stress that balances the compressive stress in the wafer, thereby resolving the contradiction between providing protection and avoiding stress-induced damage
2Ease of manufacture
If a single-layer passivation film is formed to provide protection, then the manufacturing process is simple, but the stress distribution is insufficient to prevent warping and cracking
Solution Approach 1:
The passivation film is divided into multiple sub-layers with different stress characteristics. The first sub-layer generates tensile stress to counteract wafer compression, while the second sub-layer provides additional protection. This segmentation allows for better stress management while maintaining manufacturing feasibility through sequential deposition
Solution Approach 2:
The invention uses a composite passivation film structure with multiple sub-layers having different material compositions and stress properties. This composite approach enables fine-tuning of the overall stress state to achieve optimal balance between preventing warping/cracking and maintaining ease of manufacture
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 tensile stress in the passivation film reduces warping of the semiconductor wafer and prevents cracks, while maintaining insulating properties and moisture resistance.
Implementation Method 1
the passivation film is formed by alternately stacking a first insulation film that has larger tensile stress and a second insulation film that has small tensile stress, and the passivation film as a whole generates tensile stress
Implementation Method 2
The wafer tends to have residual compressive stress due to the differences in the thermal expansion coefficient between various materials
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a semiconductor element formed in or on the semiconductor substrate, a metal layer connected to the semiconductor element, and a passivation film that protects the semiconductor element. The passivation film is formed by alternately stacking a first insulation film that has larger tensile stress and a second insulation film that has smaller tensile stress. Each of the first insulation film and the second insulation film is one of a silicon nitride film, a silicon oxide film, and a silicon oxynitride film. The passivation film as a whole generates tensile stress.