Under Bump Metal Film Edge Positioning for Semiconductor Pad Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor device manufacturing techniques face challenges in preventing curling and peeling of upper layer metal films during the formation of under bump metal (UBM), which leads to electrical short circuits and contamination, especially when achieving small pitch pads for flip-chip bonding.
Innovation Solution
A manufacturing method involving a multilayer metal film structure where the edge of the upper metal film is etched to be inside or aligned with the edge of the lower metal film, using a resist mask for precise etching to prevent curling and peeling, and reducing the pitch between pads, employing a single photolithography step to enhance accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the lower layer metal film is over-etched to avoid etching residue, then the etching completeness is improved, but the upper layer metal film curls or peels causing electrical short circuits
Solution Approach 1:
The patent applies preliminary action by forming a protective film over the upper layer metal film before etching the lower layer metal film. This protective film prevents the upper layer from curling or peeling during the over-etching process, allowing complete removal of lower layer residue without causing structural damage to the upper layer.
Solution Approach 2:
The protective film acts as an intermediary element between the etching process and the upper layer metal film. It shields the upper layer from the harmful effects of over-etching while allowing the etching solution to access and remove residue from the lower layer, thus mediating between etching completeness and structural integrity.
2Reliability
If two photolithography steps are used to prevent curling and peeling, then the quality of UBM formation is improved, but the positional accuracy of patterns deteriorates
Solution Approach 1:
The patent merges the protective function with the existing upper layer metal film by forming a protective film over it, rather than using a separate photolithography step. This combines the protection function with the already-formed structure, avoiding the need for additional pattern alignment steps that would reduce positional accuracy.
Solution Approach 2:
The protective film is formed preliminarily before the etching process, establishing protection in advance without requiring subsequent photolithography steps. This preliminary protective layer enables single-step photolithography to maintain pattern positional accuracy while still preventing curling and peeling during etching.
3Productivity
If the pitch between pads is reduced for ultra-dense packing, then the device integration density is improved, but the difficulty of preventing curling and peeling increases
Solution Approach 1:
The protective film is formed preliminarily over the upper layer metal film before any etching operations, establishing a robust protection mechanism that works effectively even at reduced pitch dimensions. This preliminary protection simplifies the overall process by preventing defects without requiring additional complex steps.
Solution Approach 2:
The patent changes the physical-chemical parameters of the system by introducing a protective film with specific etching resistance properties. This parameter change enables the system to maintain structural integrity at smaller pitch dimensions, allowing ultra-dense packing without proportionally increasing process complexity.
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
This method improves the quality and reliability of semiconductor devices by preventing electrical short circuits and contamination, allowing for the achievement of smaller pitch pads with enhanced processing accuracy and reduced assembly line contamination.
Implementation Method 1
forming a resist film over the multilayer metal film
Implementation Method 2
removing a part of a first metal film as an uppermost layer of the multilayer metal film by etching
Data Source
AI summary
A semiconductor device with improved quality and reliability is provided. In a UBM formed over an electrode pad located over a semiconductor substrate, the edge (end) of an Au film as an upper layer is located inside or in the same position as the edge (end) of a TiW film as a lower layer, which can suppress the formation of a suspended part in the Au film. This arrangement can prevent the occurrence of electrical short circuit between the adjacent pads due to the suspended part and the adhesion of the suspended part as foreign matter to the semiconductor substrate, thus improving the quality and reliability of the semiconductor device (semiconductor chip).