Under-Bump Metallization Profiles for Coplanar Conductive Bumps
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is achieving improved coplanarity of conductive bumps with different widths, as the reflow of conductive material can result in uneven top surfaces, leading to issues like cold joints and solder bridges.
Innovation Solution
The solution involves forming under-bump metallizations (UBMs) with different widths, where wider UBMs have concave top surfaces and narrower UBMs have flat or convex surfaces. This is achieved through a plating process controlled by the concentration of a leveling agent and current density, ensuring that the conductive connectors formed over these UBMs have improved coplanarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conductive material is deposited and reflowed to form conductive bumps, then the conductive connectors are formed, but the top surfaces become uneven due to different UBM widths, resulting in poor coplanarity
Solution Approach 1:
The patent applies local quality by creating different surface profiles (concave vs. flat/convex) on UBMs based on their width. Wider UBMs are formed with concave top surfaces while narrower UBMs have flat or convex surfaces. This localized differentiation allows conductive material to reflow uniformly across all UBMs, achieving improved coplanarity of conductive bump top surfaces while accounting for the varying base widths.
Solution Approach 2:
The patent utilizes parameter changes in the plating process, specifically adjusting the concentration of leveling agents and current density during electroplating. By modifying these parameters, the process dynamically adapts to create the desired concave or flat/convex surface profiles on UBMs based on their width, enabling precise control over surface morphology without manual intervention.
2Productivity
If UBMs and conductive connectors are formed in separate processes, then each can be optimized independently, but production time increases
Solution Approach 1:
The patent merges the UBM formation and conductive connector formation into a single integrated electroplating process. By combining these steps, the patent reduces production time and increases throughput. The integration is made possible because the plating parameters can be controlled to first form the UBM with the appropriate surface profile, then continue plating to create the conductive connector on top, all in one continuous operation.
Solution Approach 2:
The patent applies preliminary action by forming the UBM with its specific surface profile (concave or flat/convex) as a preparatory step before the conductive connector formation. This preliminary shaping of the UBM surface ensures that subsequent conductive material deposition and reflow will result in coplanar bump tops. The surface profile is established in advance to guide the final morphology of the conductive connectors.
3Manufacturing precision
If uniform UBMs are used for all conductive connectors, then the process is simpler, but coplanarity cannot be achieved when connectors have different widths
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting leveling agent concentration and current density during the electroplating process based on UBM width. This allows the formation of different surface profiles (concave for wide UBMs, flat or convex for narrow UBMs) using a single unified process, rather than requiring separate processes for different UBM types. The parameters are modified in response to the specific geometry being formed.
Solution Approach 2:
The patent applies self-service by allowing the electroplating process to automatically adapt and create the appropriate surface profile based on the UBM width. The plating parameters and leveling agents work autonomously to detect and respond to the varying widths, generating the correct concave or flat/convex profile without external intervention or complex additional processing steps.
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 approach enhances the coplanarity of conductive bumps, reduces yield loss due to defects like cold joints and solder bridges, and increases production efficiency by allowing simultaneous formation of UBMs and conductive connectors, thereby reducing production time and costs.
Implementation Method 1
This is achieved through a plating process controlled by the concentration of a leveling agent and current density
Data Source
AI summary
Methods for forming under-bump metallurgy (UBM) structures having different surface profiles and semiconductor devices formed by the same are disclosed. In an embodiment, a semiconductor device includes a first redistribution line and a second redistribution line over a semiconductor substrate; a first passivation layer over the first redistribution line and the second redistribution line; a first under-bump metallurgy (UBM) structure over and electrically coupled to the first redistribution line, the first UBM structure extending through the first passivation layer, a top surface of the first UBM structure being concave; and a second UBM structure over and electrically coupled to the second redistribution line, the second UBM structure extending through the first passivation layer, a top surface of the second UBM structure being flat or convex.