Metal Dam in Semiconductor Chip-on-Chip Packaging
Solution Overview
Problem
In chip-on-chip (COC) packaging, excessive underfill flow can cover bond pads around the circumference of semiconductor dies, preventing wire bonding due to the lack of effective containment mechanisms.
Innovation Solution
A semiconductor device with a metal dam formed between the bond pads and metal pillars on the first semiconductor die, which prevents underfill from bleeding out and protects the bond pads, using conductive bumps to connect metal pillars between dies and a substrate, and metal plating to form the dam and bumps simultaneously, eliminating the need for additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill is injected into the gap between semiconductor dies, then the gap is filled and structural support is provided, but the underfill may flow excessively in the circumferential direction and cover the bond pads
Solution Approach 1:
A dam structure is introduced as an intermediary element between the underfill and the bond pads. The dam acts as a physical barrier that mediates the interaction between the flowing underfill and the bond pad region, preventing the underfill from covering the bond pads while still allowing the underfill to provide structural support in the gap region.
Solution Approach 2:
The gap region is segmented into different zones by introducing the dam structure. The dam divides the continuous gap into regions with different underfill flow characteristics, allowing controlled underfill presence in some areas while preventing underfill intrusion into the bond pad region.
2Ease of manufacture
If conventional packaging methods are used without additional containment structures, then the manufacturing process is simple, but there is no mechanism to prevent underfill from covering bond pads
Solution Approach 1:
The dam structure is formed simultaneously with the metal pillars through a single plating process. By merging the formation of these two structures into one step, the solution maintains manufacturing simplicity while providing the necessary underfill containment function.
Solution Approach 2:
The plating structure serves multiple functions: it provides mechanical support, enables electrical connection through conductive bumps, and prevents underfill flow. This multi-functional approach eliminates the need for separate containment structures, maintaining process simplicity while ensuring wire bonding capability.
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 metal dam effectively prevents underfill from covering bond pads, ensuring successful wire bonding and improving the form factor of the semiconductor device by maintaining the structural integrity and preventing short-circuiting during high-temperature processing.
Implementation Method 1
A conductive bump connects the at least one metal pillar of the first semiconductor die to the at least one metal pillar of the second semiconductor die
Implementation Method 2
metal plating to form the dam and bumps simultaneously
Data Source
AI summary
A semiconductor device is disclosed that may include a first semiconductor die comprising a copper pillar, a second semiconductor die comprising a copper pillar, and a conductive bump connecting the copper pillar of the first semiconductor die to the copper pillar of the second semiconductor die. The first semiconductor die may comprise a metal dam formed between the copper pillar and a bond pad on the first semiconductor die. The conductive bump may have a melting point lower than melting points of the copper pillar of the first semiconductor die and the copper pillar of the second semiconductor die. The first semiconductor die may be coupled to a substrate with a conductive wire coupled to the bond pad and to the substrate. The first semiconductor die may comprise a redistribution layer formed beneath the copper pillar on the first semiconductor die.