Sacrificial Pad Structure for Probe-Mark-Free Wafer Testing
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Solution Overview
Problem
The formation of probe marks on conductive pads during wafer testing in semiconductor manufacturing leads to reduced surface flatness, increasing the risk of delamination of dielectric layers and potential device failure.
Innovation Solution
The implementation of a sacrificial test structure, comprising a sacrificial pad and via, which is used during wafer testing to avoid direct contact with the conductive pads, followed by removal of the structure to maintain pad flatness and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If probe contact is used during wafer testing to test conductive pads, then electrical testing can be performed, but probe marks are formed that reduce surface flatness and increase delamination risk
Solution Approach 1:
A sacrificial test structure comprising a sacrificial pad and sacrificial via is introduced as an intermediary element. The probe contacts the sacrificial pad instead of the conductive pad, and the sacrificial via provides the electrical connection through the passivation layer. This mediator transfers the testing function away from the conductive pad, preventing probe marks while maintaining testing capability.
Solution Approach 2:
The sacrificial test structure is designed as a temporary, disposable component that is removed after wafer testing. The sacrificial pad and via serve their purpose during testing and are then eliminated, leaving no permanent damage to the conductive pad. This disposable approach sacrifices a temporary structure to protect the permanent conductive pad.
2Productivity
If probe marks are formed on conductive pads, then wafer testing can be completed, but the risk of dielectric layer delamination increases
Solution Approach 1:
The sacrificial test structure acts as an intermediary that absorbs the mechanical stress of probe contact. By directing probe forces to the sacrificial pad and via rather than the conductive pad, the structural integrity of the dielectric layers remains intact, preventing delamination while still enabling testing completion.
Solution Approach 2:
The sacrificial test structure provides beforehand cushioning by absorbing the impact and stress of probe contact before it can reach the conductive pad and dielectric layers. This pre-positioned protective structure prevents the harmful effects of probe marking and potential delamination.
3Manufacturing precision
If a sacrificial test structure is used during wafer testing, then probe marks on conductive pads are avoided, but additional manufacturing steps are required
Solution Approach 1:
The sacrificial pad and sacrificial via are formed as an integrated test structure in combination with the existing passivation layer. The sacrificial via extends through the passivation layer to contact the conductive pad, while the sacrificial pad sits on the passivation layer surface. This merged structure is created using standard semiconductor fabrication processes, adding functionality without requiring entirely new process equipment or methods.
Data Source
AI summary
A method of forming a semiconductor device includes: forming a conductive pad over and electrically coupled to an interconnect structure, where the interconnect structure is disposed over a substrate and electrically coupled to electrical components formed on the substrate; forming a passivation layer over the conductive pad and the interconnect structure; and forming a sacrificial test structure over the passivation layer and electrically coupled to the conductive pad, where the sacrificial test structure includes a sacrificial pad extending along an upper surface of the passivation layer distal from the substrate, and includes a sacrificial via extending into the passivation layer and contacting the conductive pad.