Wafer Level Package Redistribution Layer Etch Masking
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Solution Overview
Problem
Conventional wafer level packaging methods experience undercuts and separation issues during wet etching of the seed metal layer, leading to unreliable redistribution interconnection metal layers due to isotropic etching and air bubble formation.
Innovation Solution
A second insulating layer is provided to shield the redistribution interconnection metal layer from chemical etchants during wet etching, and its reduced thickness facilitates patterning to prevent undercuts and separation, ensuring reliable adhesion and bubble-free formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is performed on the seed metal layer to remove unwanted portions, then the seed metal layer can be selectively removed, but the redistribution interconnection metal layer may be undercut and separated from the substrate
Solution Approach 1:
A second insulating layer is introduced as an intermediary protective layer between the etchant and the redistribution interconnection metal layer. This layer acts as a mask during wet etching of the seed metal layer, preventing direct contact between the etchant and the metal layer, thereby avoiding undercut and separation while still allowing complete removal of unwanted seed metal portions
Solution Approach 2:
The second insulating layer is formed on the redistribution interconnection metal layer before the wet etching process. This preliminary protective action ensures that the metal layer is shielded from etchant exposure during subsequent etching operations, preventing adhesion failure and undercut issues
2Ease of manufacture
If isotropic etching is used to remove the seed metal layer, then complete removal can be achieved, but air bubbles are trapped and cause separation of the insulating layer
Solution Approach 1:
The second insulating layer serves as a protective barrier that prevents air bubbles trapped during etching from causing direct separation of the first insulating layer from the redistribution metal layer. Even if bubbles form during isotropic etching, they are contained between the metal layer and the protective second insulating layer, maintaining overall structure integrity
Solution Approach 2:
The second insulating layer provides a cushioning protective effect before the etching process occurs. This pre-established protective layer absorbs and isolates the harmful effects of air bubble formation and etchant exposure, preventing direct damage to the adhesion between functional layers
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 solution prevents undercuts and separation of the redistribution interconnection metal layer from the substrate, enhancing the reliability and stability of the wafer level package by using the second insulating layer as an etch mask and reducing bubble formation.
Implementation Method 1
The redistribution interconnection metal layer 40 may be formed by electrical plating, for example
Implementation Method 2
unwanted portions of the seed metal layer 30 may be removed via a wet etching process
Data Source
AI summary
A wafer level package may include a semiconductor substrate supporting an electrode pad. A first insulating layer may be provided on the semiconductor substrate. The first insulating layer may include a first opening through which the electrode pad may be exposed. A seed metal layer may be provided on an entire surface of the first insulating layer. A redistribution interconnection metal layer may be provided on the seed metal layer. A second insulating layer may be provided on the redistribution interconnection metal layer. The second insulating layer may have a second opening spaced from the first opening to expose a portion of the redistribution interconnection metal layer. The second insulating layer may surround the redistribution interconnection metal layer. An unwanted portion of seed metal layer may be removed using the second insulating layer as an etch mask.