High-Temperature Isotropic Plasma Etching for Titanium Nitride
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Solution Overview
Problem
Conventional etching processes for metal stacks in auto-focus lenses, such as those used in MEMS devices, often result in electrical shorts due to the presence of stringers from titanium nitride residue, and fail to effectively prevent moisture ingress, which can reduce the breakdown voltage of the capacitor and interfere with device operation.
Innovation Solution
A high-temperature isotropic plasma etching process using a gas mixture of tetrafluoromethane (CF4) and oxygen (O2) at temperatures above 200°C, with specific flow rates and RF power, is employed to etch through titanium nitride and titanium layers, removing stringers and preventing oxide film formation, while the aluminum copper layer acts as a hardmask during the dry etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching processes are used to etch metal stacks, then the etching process can be completed, but electrical shorts occur due to stringers from titanium nitride residue
Solution Approach 1:
The patent changes the etching parameters by using a gas mixture of CF4 and O2 at temperatures above 200°C, which transforms the etching mechanism to prevent titanium nitride stringer formation while maintaining etching effectiveness through the aluminum copper hardmask layer
Solution Approach 2:
The patent converts the potential harm of titanium nitride residue into a benefit by using the aluminum copper layer as a hardmask that prevents stringer formation, turning a problematic material interaction into a solution that eliminates electrical shorts
2Productivity
If conventional etching processes are used, then the etching can proceed, but moisture ingress occurs which reduces breakdown voltage
Solution Approach 1:
The patent creates an inert environment by using a CF4 and O2 gas mixture during etching at elevated temperatures, which prevents moisture ingress and oxide film formation on the metal surfaces, thereby maintaining breakdown voltage and preventing capacitor degradation
3Productivity
If conventional etching processes are used, then etching can be performed, but oxide film formation interferes with device operation
Solution Approach 1:
The patent changes the chemical environment by introducing O2 into the etching gas mixture and maintaining temperatures above 200°C, which prevents oxide film formation on the metal surfaces during the CF4-based etching process, ensuring device operation is not interfered with
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 process effectively prevents electrical shorts, increases the breakdown voltage by blocking moisture, and facilitates easier testing and assembly by preventing surface reactions, thereby enhancing the reliability and performance of the auto-focus lens.
Implementation Method 1
performing an etching process using the chamber to etch through portions of the titanium nitride layer. Performing the etching process includes flowing a gas mixture containing tetrafluoromethane and oxygen gas into the chamber at a temperature of at least about 200° C.
Implementation Method 2
flowing a gas mixture containing tetrafluoromethane and oxygen gas into the chamber at a temperature of at least about 200° C.
Implementation Method 3
performing an ashing process on the mask using the chamber
Data Source
AI summary
A method includes placing a device having a titanium nitride layer into a chamber. The device also has a mask that includes a photoresist material and an aluminum copper hardmask. The method also includes performing an ashing process on the mask using the chamber. The method further includes, after the ashing process, performing an etching process using the chamber to etch through portions of the titanium nitride layer. Performing the etching process includes flowing a gas mixture containing tetrafluoromethane (CF4) and oxygen gas (O2) into the chamber at a temperature of at least about 200° C.