Semiconductor Contact Metallization Double Lift-Off Process
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Solution Overview
Problem
Conventional semiconductor chip fabrication techniques face challenges in forming stable electrical contact layers due to the vulnerability of materials used for environmental resistance, which limits their thickness and effectiveness in providing reliable connections.
Innovation Solution
A double lift-off technique is employed, involving a first lift-off process to form a layer stack with good adhesion and conductivity, followed by a second lift-off process that encases the first layer stack, providing corrosion resistance and increased thickness, thus enhancing the mechanical stability and reliability of electrical contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single lift-off process is used to form a protection layer, then the fabrication process is simple, but the layer thickness is limited and electrical contact stability is insufficient
Solution Approach 1:
The fabrication process is divided into two separate lift-off processes: a first lift-off process forms an initial layer structure, and a second lift-off process forms an additional protection layer. This segmentation allows each process to be optimized independently, achieving both manufacturing feasibility and reliable electrical contact stability through cumulative layer thickness.
2Ease of manufacture
If conventional etching is used to form layers, then material processing is straightforward, but environmental resistance is poor and deterioration occurs
Solution Approach 1:
A protective layer is formed in advance during the second lift-off process to encase and protect vulnerable materials from environmental influences before subsequent processing steps. This preliminary protection prevents oxidation and deterioration of etched materials while maintaining the ease of conventional etching processes.
3Reliability
If a thick protection layer is formed to ensure stability, then electrical contact reliability improves, but the lift-off process becomes limited by mask thickness
Solution Approach 1:
The thick protection structure is achieved by segmenting the deposition into two stages: the first lift-off process creates a base layer structure, and the second lift-off process adds the remaining thickness. This circumvents the mask thickness limitation of a single lift-off process while achieving the required total thickness for reliable electrical contact.
4Object-affected harmful factors
If multiple process steps are added to form environmental resistant layers, then protection quality improves, but fabrication complexity and process time increase
Solution Approach 1:
The second lift-off process simultaneously achieves multiple objectives: it forms additional protection layer material, provides environmental resistance to vulnerable layers, and maintains compatibility with conventional fabrication workflows. By combining these functions into a single integrated process step, the invention improves environmental resistance without proportionally increasing fabrication complexity.
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 double lift-off technique results in a robust contact pad metallization that is both corrosion-resistant and solderable, offering improved process windows for interconnect techniques and increased mechanical stability, overcoming the limitations of single lift-off processes.
Implementation Method 1
a layer is deposited on a structured mask which is used as sacrificial layer and removed together with the unwanted parts of the layer (also referred to as lift-off process)
Data Source
AI summary
According to various embodiments, a method may include: forming a first layer on a surface using a first lift-off process; forming a second layer over the first layer using a second lift-off process; wherein the second lift-off process is configured such that the second layer covers at least one sidewall of the first layer at least partially.