Electrode Layer Spacing for Passivation Film Crack Prevention
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Solution Overview
Problem
In semiconductor device manufacturing, the passivation film cracks due to stress concentration at stepped portions when a conductive member is coupled to a bonding pad, especially when the alignment is off, leading to reliability issues and potential corrosion.
Innovation Solution
The method involves forming an electrode layer that overlaps the bonding pad and the passivation film, with a larger distance between the electrode layer and the pad compared to the electrode layer and the opening, to distribute stress and prevent cracking, even when the conductive member is misaligned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening is formed smaller than the bonding pad to prevent corrosion, then corrosion resistance is improved, but alignment accuracy requirement increases
Solution Approach 1:
An electrode layer is introduced as an intermediary between the bonding pad and the conductive member. This electrode layer extends from the exposed bonding pad region onto the passivation film, creating a transition zone that mediates between the small opening (for corrosion prevention) and the bonding pad (for electrical connection). The electrode layer allows the opening to remain small while providing sufficient alignment tolerance through its extended structure on the passivation film.
2Ease of operation
If the electrode layer extends over the passivation film end portion to improve alignment tolerance, then alignment ease is improved, but stress concentration at stepped portions increases
Solution Approach 1:
The electrode layer is designed with spatially varying functions: in the region over the bonding pad, it provides electrical connection; in the region over the passivation film, it provides alignment tolerance. The passivation film thickness is specifically controlled in the region under the electrode layer's end portion to reduce stress concentration. This local differentiation of properties allows the electrode layer to extend beyond the opening without causing cracking.
Solution Approach 2:
The passivation film thickness parameter is specifically adjusted in the region where the electrode layer extends beyond the opening. By making the passivation film thinner in this specific region (compared to other regions), the stress concentration at the stepped portion is reduced, preventing crack formation while maintaining the electrode layer's alignment-tolerance function.
3Strength
If the passivation film is made thicker to prevent cracking, then structural strength is improved, but opening depth and stepped portion depth increase
Solution Approach 1:
Instead of increasing the passivation film thickness throughout to prevent cracking (which would deepen the opening and stepped portion), the approach is inverted: the passivation film is made thinner in the specific region where the electrode layer extends beyond the opening. This local thinning reduces stress concentration and prevents cracking, while the opening depth remains controlled. The electrode layer's extended structure compensates for the reduced passivation film thickness.
Data Source
AI summary
A semiconductor device has a conductive member coupled to the surface of a bonding pad exposed from an opening formed in a passivation film. A second planar distance between a first end of an electrode layer and a first end of a bonding pad is greater than a first planar distance between the first end of the electrode layer and a first end of an opening. Since the second planar distance between the first end of the electrode layer and the first end of the bonding pad is long, even when a coupled position of wire is deviated to the first end side of the electrode layer, stress caused by coupling of the wire to a stepped portion of the electrode layer can be prevented from being transmitted to the first end portion of the bonding pad.