Selective ENEPIG Contact Stack for Reliable Semiconductor Wire Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor fabrication processes face connectivity issues due to undesirable alloy formation between wire bonds and stacked conductive layers, leading to unreliable connections, particularly in automotive applications where reliability is critical.
Innovation Solution
The selective formation of a stacked conductive layer, such as an Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) layer, is achieved by excluding its formation on specific conductive contacts, using polyimide layers to isolate and protect these contacts from the stacked layer, ensuring direct metal connections during wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stacked conductive layer is formed on all conductive contacts, then the electrical connectivity and solderability are improved, but undesirable alloy formation occurs between the stacked layer and wire bonds, reducing connection reliability
Solution Approach 1:
The patent applies different surface treatments to different conductive contacts based on their specific function. Power and ground contacts receive the full stacked conductive layer (ENEPIG) for enhanced solderability, while bond pads are kept as pure aluminum to enable reliable wire bonding. This localized differentiation resolves the contradiction by providing the right surface properties in the right locations.
Solution Approach 2:
The conductive contacts are segmented into two categories: those requiring stacked conductive layers (power/ground) and those requiring direct metal exposure (bond pads). The masking process segments the deposition area, allowing selective formation of the ENEPIG stack only on designated contacts, preventing harmful alloy formation while maintaining necessary connectivity.
2Reliability
If a stacked conductive layer is formed to enhance electrical connectivity, then the manufacturing process complexity increases due to additional masking and deposition steps
Solution Approach 1:
The patent performs preliminary planning of contact classifications before deposition. Conductive contacts are pre-categorized into stacked-layer-receiving and direct-wire-bonding zones using masking layers that are formed before the ENEPIG deposition. This preliminary action organizes the complexity into manageable steps, reducing overall manufacturing complexity while ensuring reliable electrical connectivity where needed.
Data Source
Figure 1~2A
Figure 2B
Figure 3A~3B
AI summary
A device may include an insulating layer disposed on a frontside of a semiconductor layer, and may include a first conductive contact disposed in a first opening in the insulating layer. The device may include a second conductive contact disposed in a second opening in the insulating layer, and may include a stacked conductive layer disposed on the first conductive contact and excluded from the second conductive contact.