Copper Bump Electrodeposition Chemistry for Distal Shape Control
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Solution Overview
Problem
Existing electrodeposition processes for copper bumps or pillars in semiconductor packaging face challenges in controlling the configuration of the distal end, leading to issues like doming, dishing, and irregular shapes, which affect productivity and bonding with solder, while current density limitations hinder efficient manufacturing.
Innovation Solution
A composition and process using a plating solution comprising copper ions, an acid, a leveler (quaternized poly(epihalohydrin), and an accelerator to electrodeposit copper bumps or pillars with controlled vertical growth, ensuring a suitable distal configuration and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional copper deposition processes are used, then existing manufacturing capabilities are maintained, but manufacturing precision deteriorates due to inability to form vias smaller than 10 micrometers
Solution Approach 1:
The patent changes the chemical parameters of the deposition process by using a semi-solid slurry containing copper particles, organic vehicle, and surfactants instead of conventional gaseous or liquid copper sources. This parameter change enables precise control of copper deposition at the via level, achieving via sizes below 10 micrometers while maintaining manufacturability through screen printing and dip printing techniques.
Solution Approach 2:
The patent introduces an organic vehicle and surfactant as intermediaries to facilitate copper deposition. The organic vehicle (such as terpineol or ethyl lactate) serves as a carrier for copper particles, while surfactants (like Triton X-100 or Igepal CO-520) act as mediators to control wetting, prevent agglomeration, and enable precise deposition. These intermediaries allow the copper slurry to be deposited through conventional printing methods while achieving precise via formation.
2Manufacturing precision
If copper is deposited in a solid state, then deposition precision is improved, but copper distribution uniformity worsens due to clogging of screen printing apertures
Solution Approach 1:
The patent changes the physical state parameter of copper from solid particles directly to a semi-solid slurry suspension. By dispersing copper particles in an organic vehicle with appropriate viscosity and adding surfactants, the slurry maintains flowability for uniform distribution while allowing precise deposition control. This parameter change prevents clogging of screen printing apertures while achieving controlled copper placement.
Solution Approach 2:
The patent applies local quality by creating a slurry with specific local properties - copper particles concentrated in regions requiring deposition while the organic vehicle and surfactants provide uniform distribution throughout the slurry. The surfactant concentration and particle size distribution are locally optimized to prevent agglomeration and ensure uniform copper distribution after deposition, while maintaining the ability to control deposition patterns through screen opening geometries.
3Manufacturing precision
If conventional printing methods are used, then device complexity is reduced, but manufacturing precision worsens due to inability to form precise via structures
Solution Approach 1:
The patent changes the material state parameter to semi-solid slurry, which enables conventional screen printing and dip printing methods to achieve via structures with dimensions below 10 micrometers. The slurry's rheological properties (viscosity, particle size distribution, surfactant concentration) are optimized to work with standard printing equipment, avoiding the need for complex specialized deposition systems while achieving high precision via formation.
Solution Approach 2:
The organic vehicle and surfactant act as intermediaries that enable conventional printing methods to achieve precise via structures. The surfactant controls the slurry's interaction with the substrate and screen printing aperture edges, ensuring clean deposition patterns. The organic vehicle maintains appropriate viscosity for screen printing while allowing complete fill of via structures. These intermediaries bridge the gap between simple conventional printing equipment and the requirement for precise sub-10-micrometer via formation.
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 process enables the formation of copper bumps or pillars with uniform and suitable distal configurations, enhancing productivity and bonding with solder, while achieving higher current densities and reducing manufacturing costs.
Implementation Method 1
The copper-containing slurry is deposited onto the substrate through screen printing or dip printing
Implementation Method 2
The copper-containing slurry is deposited onto the substrate through screen printing or dip printing
Implementation Method 3
The deposited copper is then sintered to form a conductive pathway between pads
Implementation Method 4
comprised of copper particles, an organic vehicle, and a surfactant
Data Source
AI summary
An electrodeposition composition comprising: (a) a source of copper ions; (b) an acid; (c) a suppressor; and (d) a leveler, wherein the leveler comprises a quaternized dipyridyl compound prepared by reacting a dipyridyl compound with a difunctional alkylating agent or a quaternized poly(epihalohydrin). The electrodeposition composition can be used in a process for forming a copper feature over a semiconductor substrate in wafer level packaging to electrodeposit a copper bump or pillar on an underbump structure of a semiconductor assembly.