Fine-Pitch Microbump Structure With Dual-Metal Bonding Layers
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Solution Overview
Problem
The miniaturization and high-density trends in semiconductor devices require more reliable connection pads, specifically finer pitch microbumps, which current technologies struggle to stabilize effectively.
Innovation Solution
A semiconductor device design featuring a conductive substrate with individual elements, interconnection structures, and connection pads with distinct bumps having different upper and lower conductive layers, where the first bump includes a tin-silver alloy and the second bump includes a nickel-tin or copper-tin alloy, ensuring structural stability through intermetallic compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If connection pads are formed with finer pitch for miniaturization and high density, then device integration density is improved, but manufacturing precision and reliability of microbumps deteriorate
Solution Approach 1:
The microbump structure is segmented into multiple functional layers: a lower conductive layer (Ni or Cu) for electrical connection and structural stability, and an upper conductive layer (Sn or Sn-based alloy) for bonding functionality. This segmentation allows each layer to be optimized independently for its specific function, enabling reliable formation of fine-pitch microbumps while maintaining manufacturing precision
Solution Approach 2:
The microbump employs composite material structure with different materials in the upper and lower layers. The lower layer uses Ni or Cu for mechanical strength and electrical conductivity, while the upper layer uses Sn or Sn-based alloys (Sn-Ag, Sn-Zn, Sn-Bi, Sn-In) for low melting point bonding capabilities. This composite approach resolves the contradiction by combining materials with complementary properties to achieve both fine pitch compatibility and manufacturing reliability
2Quantity of substance
If microbump size is reduced for finer pitch, then device density is improved, but structural stability and reliability of microbumps deteriorate
Solution Approach 1:
The composite microbump structure with Ni/Cu lower layer and Sn-based upper layer provides enhanced structural stability even at reduced sizes. The Ni or Cu lower layer offers high mechanical strength and structural integrity, while the Sn-based upper layer maintains bonding functionality. This composite design allows microbumps to be scaled down for higher device density while preserving structural stability through the synergistic combination of materials
Solution Approach 2:
Different regions of the microbump are assigned different material properties: the lower layer near the substrate provides structural support and electrical connection, while the upper layer at the bonding interface provides low-temperature bonding capability. This local differentiation of material quality allows the microbump to maintain structural stability at finer pitches by optimizing each region's material properties for its specific functional requirements
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a connection pad disposed on an interlayer insulating layer and electrically connected to an interconnection structure, a passivation layer disposed on the connection pad and having a first opening and a second opening, each exposing at least a portion of the connection pad, a first bump that includes a first lower conductive layer in contact with the connection pad within the first opening and a first upper conductive layer on the first lower conductive layer, and a second bump that includes a second lower conductive layer in contact with the connection pad within the second opening and a second upper conductive layer on the second lower conductive layer. The first and second lower conductive layers include the same material, and the first upper conductive layer and the second upper conductive layer include different materials.