MEMS Trench Width Control via Dielectric Anti-Reflective Coating
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Solution Overview
Problem
Conventional MEMS device fabrication processes face challenges in controlling trench width due to the reaction between the tantalum nitride layer and photoresist, leading to the formation of tantalum-containing polymeric substances that impede residue removal and can broaden the trench, affecting device performance.
Innovation Solution
A method involving the formation of a dielectric anti-reflective coating layer, such as silicon oxynitride, between the tantalum nitride layer and photoresist to prevent reaction during the ashing process, ensuring precise control over trench width and removal of residues without broadening the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intensified ashing process using CF4 and O2 is used to remove photoresist residues, then photoresist removal capability is improved, but trench width control deteriorates due to trench broadening and TaN layer peeling
Solution Approach 1:
A dielectric anti-reflective coating layer (DARC) is introduced as an intermediary layer between the TaN layer and photoresist. This DARC layer acts as a protective mediator that prevents direct contact and harmful reactions between CF4/O2 plasma and the TaN layer during intensified ashing, thereby maintaining trench width precision while enabling effective photoresist removal
Solution Approach 2:
The dielectric anti-reflective coating layer is formed in advance before photoresist coating and etching processes. This preliminary action establishes a protective barrier that prevents trench broadening and TaN layer peeling during subsequent intensified ashing operations, enabling aggressive photoresist removal without compromising trench dimensions
2Ease of manufacture
If conventional ashing process with pure oxygen at 250°C is used, then process simplicity is maintained, but photoresist and BARC residue removal is insufficient due to tantalum-containing polymeric substances formation
Solution Approach 1:
The dielectric anti-reflective coating layer serves as a protective intermediary that prevents TaN layer reaction with photoresist during ashing. By eliminating the formation of tantalum-containing polymeric substances, this intermediary layer enables complete residue removal while maintaining process simplicity
Solution Approach 2:
The invention converts the potentially harmful reaction between TaN layer and photoresist (which forms polymeric substances) into a beneficial situation. By introducing the DARC layer, the harmful reaction is prevented, and the ashing process can proceed cleanly without generating problematic residues, thereby improving removal efficiency
3Manufacturing precision
If trench width is strictly controlled within 0.2 μm to 0.5 μm, then MEMS device performance is improved, but process complexity increases due to multiple protective layers and precise etching requirements
Solution Approach 1:
The dielectric anti-reflective coating layer performs multiple functions simultaneously: it serves as a protective barrier preventing TaN layer reaction with photoresist, acts as an etch stop layer to define trench depth, and provides a uniform surface for photoresist coating. This multi-functionality enables precise trench width control without proportionally increasing process 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 method effectively prevents the formation of tantalum-containing polymeric substances, allowing for successful removal of photoresist and anti-reflective coating residues while maintaining the trench width within the required range of 0.2 μm to 0.5 μm, thereby enhancing the performance of the MEMS device.
Implementation Method 1
the dielectric anti-reflective coating layer prevents the tantalum nitride layer from reacting with the photoresist to form tantalum-containing polymeric substances during the intensified ashing process
Implementation Method 2
performing an intensified ashing process and a wet cleaning process to remove the photoresist pattern and the dielectric anti-reflective coating layer
Data Source
AI summary
A method of forming a micro-electro-mechanical systems (MEMS) device includes: providing a substrate; forming a tantalum nitride (TaN) layer on the substrate; forming a dielectric anti-reflective coating (DARC) layer on the TaN layer; coating photoresist on the DARC layer and etching the DARC: and TaN layers to form a trench; performing intensified ashing and wet cleaning processes to remove the photoresist and the DARC layer. The DARC layer can prevent the formation of tantalum-containing polymeric substances from a reaction between the TaN layer and the photoresist during the intensified ashing process.