Nitric-Based Etchant for Solder Cap Removal in Semiconductor Devices
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Solution Overview
Problem
In semiconductor device manufacturing, the removal of solder caps from conductive features using traditional etching processes often results in surface damage and delamination issues during subsequent encapsulation steps, affecting the adhesion and reliability of the encapsulant with the conductive features.
Innovation Solution
The use of a nitric-based etchant for selective etching of solder caps from conductive features, which reduces delamination and improves surface cleanliness, thereby enhancing the adhesion between the encapsulant and the conductive features, particularly when using low-temperature polyimide encapsulants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional etching processes are used to remove solder caps from conductive features, then the solder caps can be removed, but surface damage and delamination issues occur during subsequent encapsulation steps
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a nitric-based etchant with specific concentration and composition ratios. This chemical parameter change enables selective removal of solder caps while preserving the conductive feature surfaces, eliminating surface damage and delamination issues that occur with traditional etching processes.
Solution Approach 2:
The nitric-based etchant acts as an intermediary substance that selectively interacts with the solder cap material while being non-damaging to the conductive features. This intermediary chemical agent facilitates the removal of solder caps without causing the harmful surface damage and delamination that would otherwise occur during the etching process.
2Ease of manufacture
If high-temperature solder removal is used, then solder caps can be removed effectively, but warpage occurs in the conductive features
Solution Approach 1:
The patent replaces the thermal/mechanical solder removal process with a chemical etching process using nitric-based etchant. This substitution eliminates the high-temperature heating step that causes thermal expansion and subsequent warpage, while still achieving effective solder cap removal through selective chemical dissolution.
Solution Approach 2:
The patent changes the process parameters from high-temperature thermal processing to ambient or controlled-temperature chemical processing. By using a nitric-based etchant at lower temperatures, the process achieves solder cap removal without the thermal stress that causes warpage in the conductive features.
3Productivity
If conventional etching methods are used, then solder caps are removed, but the process window for subsequent processing steps is reduced
Solution Approach 1:
The nitric-based etchant serves as a selective intermediary that distinguishes between solder cap material and conductive feature materials. This selectivity allows complete solder cap removal while leaving the conductive feature surfaces intact and clean, thereby expanding the process window for subsequent encapsulation and processing steps.
Solution Approach 2:
The patent modifies the etching process parameters by using a nitric-based etchant with optimized concentration and composition. This parameter change achieves complete solder cap removal while maintaining surface quality, thereby increasing the process window and flexibility for subsequent manufacturing 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 minimizes surface damage and delamination, improving the yield and reliability of semiconductor devices by ensuring better adhesion and reducing warpage caused by high-temperature solder removal, thus increasing the process window for subsequent processing steps.
Implementation Method 1
The use of a nitric-based etchant for selective etching of solder caps from conductive features
Implementation Method 2
The nitric-based etchant may clean the surface of the conductive feature such that delamination is reduced or eliminated
Data Source
AI summary
A semiconductor device and method includes forming a conductive post on a die; coupling a test probe to the conductive post with solder; and etching the solder and the conductive post with a plurality of etching processes, the plurality of etching processes including a first etching process, the first etching process comprising etching the conductive post with a nitric-based etchant.