Wiring Substrate Etching Suppresses Side Etching
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Solution Overview
Problem
The semi-additive process for manufacturing IC package substrates faces challenges in achieving finer wiring patterns due to excessive side etching of electrolytic copper wires, which is difficult to control with conventional etching methods, leading to issues with resist pattern formation and wire delamination.
Innovation Solution
A method involving a pre-etching treatment with a chloride ion-containing liquid followed by etching with a hydrogen peroxide and sulfuric acid-based composition, which adjusts the etching rates of electroless and electrolytic copper to suppress side etching, using a ratio of electroless copper to electrolytic copper etching rates of 2.1 or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the amount of side etching is decreased by adjusting etching conditions, then the manufacturing precision of fine wiring patterns is improved, but the etching rate of electroless copper becomes insufficient to remove the seed layer completely
Solution Approach 1:
The patent changes the chemical composition parameters of the etching liquid by adding specific compounds (azole, thiazole, or isothiazole) to the conventional hydrogen peroxide-sulfuric acid base. This chemical parameter modification selectively suppresses the etching rate of electrolytic copper while maintaining adequate etching of electroless copper, achieving both fine wiring pattern precision and complete seed layer removal
Solution Approach 2:
The patent applies local quality by creating different etching environments for different copper types. The added heterocyclic compounds preferentially affect electrolytic copper surfaces, creating a localized suppression of side etching at wire edges while allowing the etching process to continue effectively on electroless copper surfaces, thus addressing different requirements in different locations
2Manufacturing precision
If the pre-etching wiring pattern L/S is reduced to achieve finer post-etching patterns, then the manufacturing precision is improved, but the resist pattern formation becomes difficult due to light scattering and expansion
Solution Approach 1:
The patent applies preliminary anti-action by pre-treating the wiring pattern with a specific liquid composition containing heterocyclic compounds before the main etching process. This pre-treatment suppresses the side etching that would otherwise occur during subsequent etching steps, preventing the wire width reduction that makes fine pattern formation difficult. By counteracting the side etching effect in advance, the patent enables the use of smaller pre-etching L/S dimensions without compromising resist pattern formation
3Manufacturing precision
If the thickness of the electroless copper seed layer is decreased to reduce side etching amount, then the manufacturing precision is improved, but the uniformity of seed layer thickness becomes difficult to control
Solution Approach 1:
Instead of changing the physical parameter of seed layer thickness, the patent changes the chemical parameters of the etching environment by adding heterocyclic compounds. This allows maintaining a sufficiently thick and uniform seed layer for reliable electroless plating while achieving reduced side etching through chemical suppression during the etching process itself
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 effectively reduces side etching of the wiring pattern, enabling the formation of high-density wiring substrates with precise wire dimensions by controlling the etching rates and potentials of electroless and electrolytic copper layers.
Implementation Method 1
contacting the wiring substrate with a pre-etching treatment liquid composition containing (a) a chloride ion and (b) a water... and (2) continuously, etching the wiring substrate with an etching liquid composition containing (c) a hydrogen peroxide, (d) a sulfuric acid
Implementation Method 2
etching the wiring substrate with an etching liquid composition containing (c) a hydrogen peroxide, (d) a sulfuric acid
Implementation Method 3
contacting the wiring substrate with a pre-etching treatment liquid composition containing (a) a chloride ion
Data Source
AI summary
A method of treating a wiring substrate according to an embodiment includes, in a semi-additive process:(1) contacting the wiring substrate with a pre-etching treatment liquid composition containing a chloride ion, the wiring substrate containing a seed layer formed of an electroless copper and a wiring pattern formed of an electrolytic copper; and(2) continuously, etching the wiring substrate with an etching liquid composition containing a hydrogen peroxide, a sulfuric acid, a tetrazole, a chloride ion, a copper ion and a water.