Microbump Planarization via Polymer Reflow
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Solution Overview
Problem
Current methods for semiconductor component bonding, such as thermocompression bonding, require expensive and not universally applicable processes like chemical mechanical polishing (CMP) for planarization of microbumps, which can be challenging for certain polymer types.
Innovation Solution
A method involving a photosensitive polymer layer applied on the bonding surface and microbumps, patterned and partially removed through lithography, then heated to flow and form a reflowed polymer layer that closely adjoins microbumps without exceeding their height, eliminating the need for CMP or fly-cut planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical polishing (CMP) or fly-cut techniques are used for planarization of microbumps, then planarity of the bonding surface is improved, but manufacturing cost increases and process universality decreases
Solution Approach 1:
The patent changes the physical state and properties of the polymer material through temperature control. By heating the polymer to its melting point and maintaining it in a molten state during bonding, the polymer automatically flows to fill gaps and create a planar surface without requiring CMP or fly-cut processes. This parameter change (temperature-induced phase transition) eliminates the need for expensive planarization equipment and expertise.
Solution Approach 2:
The polymer material performs self-planarization through its own melting and flowing properties. When heated above its melting point, the polymer automatically flows to level the bonding surface, creating a planar interface without external mechanical intervention. This self-service mechanism replaces expensive CMP or fly-cut processes with a simple thermal treatment that is universally applicable.
2Manufacturing precision
If a polymer layer is applied to embed microbumps for planarization, then alignment tolerance and microbump protection are improved, but additional process steps and complexity are introduced
Solution Approach 1:
The patent merges multiple functions into the polymer layer: it serves as an embedding material for microbumps, a protective coating during handling, and a self-planarizing layer through its melting behavior. By combining these functions into a single material system, the patent reduces overall process complexity compared to separate embedding and planarization steps using CMP or fly-cut techniques.
Solution Approach 2:
The polymer layer performs multiple functions simultaneously: it embeds microbumps to improve alignment tolerance, protects microbumps during handling, and self-planarizes the bonding surface through thermal melting. This multi-functional approach eliminates the need for separate specialized processes, reducing overall device complexity while maintaining precision.
3Productivity
If microbumps are made dense with small pitch for high-density interconnection, then interconnection density is improved, but microbump fabrication difficulty and alignment precision requirements increase
Solution Approach 1:
The patent applies polymer embedding before the bonding process to create a cushioning effect. The polymer layer compensates for minor misalignments and variations in microbump heights, providing a tolerance buffer that enables successful bonding even with dense microbump arrays. This beforehand cushioning allows high interconnection density without proportionally increasing alignment precision requirements.
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 provides a cost-effective and universally applicable method for preparing semiconductor components for thermal bonding, achieving planarity equivalent to prior art methods without the need for expensive CMP or fly-cut processes, while ensuring reliable microbump alignment and bonding.
Implementation Method 1
heating the polymer layer to a temperature at which the polymer flows
Implementation Method 2
heating the polymer layer to a temperature at which the polymer flows, resulting in a polymer layer that closely adjoins the microbumps
Implementation Method 3
spin-coating of a solution comprising the polymer followed by a soft bake for removing volatile components
Data Source
Figure 1a~1e
Figure 1f~1h
AI summary
According to the method of the invention, a semiconductor component comprising microbumps (5) on a planar bonding surface is prepared for bonding by applying a photosensitive polymer layer (6) on the bonding surface. The average thickness of the initial polymer layer (6) in between the microbumps is similar to the average height of the microbumps (5). This is followed by a lithography-step wherein the polymer is removed from the upper surface of the microbumps and from areas (10,11) around microbumps. This is followed by heating to a temperature at which the polymer flows, resulting in a polymer layer (7) that closely adjoins the microbumps, without exceeding the microbump height. The closely adjoining polymer layer (7) has a sufficient degree of planarity to make it equivalent to a planarized layer obtainable by prior art methods. The invention is equally related to a method for bonding the thus prepare component..