Integrated Etching Device for MEMS Sacrificial Layer Removal
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Solution Overview
Problem
Current etching methods for micromechanical structures, particularly those using silicon sacrificial layers, face limitations in etching rate and efficiency due to the need for multiple separate modules and handling steps, leading to increased costs, long process durations, and risks of product damage.
Innovation Solution
An etching device that combines plasma-assisted and plasma-free etching methods, utilizing a movable gas nozzle distribution device and chuck to optimize etching conditions, allowing for isotropic and anisotropic etching processes, including the removal of natural oxide, to achieve high etching rates and prevent etching delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma-free etching methods are used for high-volume sacrificial structures, then selectivity is improved (up to 1000), but volume etching rate is low (typically 11 mm³/min)
Solution Approach 1:
The patent combines plasma-free etching (for high selectivity) and plasma-assisted etching (for high volume etching rate) into a single integrated etching device. The device can switch between the two methods or use them in sequence, allowing the system to achieve both high selectivity and high productivity that neither method can achieve alone.
2Productivity
If plasma-assisted etching is used for high-volume sacrificial structures, then volume etching rate is improved (>500 mm³/min), but etching rate drops as distance to access opening increases
Solution Approach 1:
The integrated device combines plasma-free and plasma-assisted etching methods to compensate for the distance-dependent rate drop in plasma-assisted etching. The plasma-free method can be used in conjunction or alternation to maintain uniform etching rates across structures with varying distances from access openings.
3Adaptability or versatility
If multiple separate etching modules are used for different etching methods, then etching versatility is improved, but process duration is long and handling steps increase
Solution Approach 1:
The patent integrates multiple etching methods (plasma-free and plasma-assisted) into a single etching device with a unified chamber and control system. This eliminates the need for separate modules and intermediate handling steps, reducing process duration while maintaining the versatility to perform different etching methods as needed.
Solution Approach 2:
The etching device is designed as a universal system capable of performing both plasma-free and plasma-assisted etching methods, as well as both isotropic and anisotropic etching modes, within a single integrated platform. This multi-functionality eliminates the need for multiple specialized modules.
4Volume of moving object
If sacrificial layer thickness is increased to accommodate functional requirements, then functional performance is improved, but etching time increases due to limited etching rate
Solution Approach 1:
By combining plasma-free etching (high selectivity) and plasma-assisted etching (high volume etching rate) in a single integrated device, the system can efficiently remove thick sacrificial layers without proportionally increasing etching time. The synergistic combination allows faster removal of large volumes while maintaining precision.
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
Enables efficient and high-rate isotropic removal of sacrificial structures with reduced process steps and costs, preventing etching delays by integrating plasma-assisted and plasma-free etching in a single device, suitable for complex MEMS structures with minimal product damage risk.
Implementation Method 1
a gas nozzle distribution device 10 through which an etching gas stream GS is delivered
Implementation Method 2
plasma generating device C which surrounds a constricted area 1a of the etching chamber 1
Implementation Method 3
with the aid of a biasing device B, with the aid of which a desired electrical potential can be applied to the chuck C
Implementation Method 4
Connected to etching chamber 1 is a pump device P for producing a desired process pressure and for pumping off the etching gas
Implementation Method 5
an actuator to move the gas nozzle distribution device 10 with respect to the wafer surface OF
Implementation Method 6
the free fluorine radicals etch silicon spontaneously, while common mask materials such as SiO2, Si3N4, SiON, silicon-rich nitrides or metals such as Al are etched very slowly
Implementation Method 7
Plasma-assisted isotropic etching using fluorine compounds such as F2, SF6, CF4 or NF3 is also suitable for the removal of buried sacrificial material. In this case, the fluorine compound is activated in the plasma; the free fluorine radicals etch silicon spontaneously
Implementation Method 8
in order to create optimized etching conditions, in particular in plasma-free etching, a movable gas nozzle distribution device (showerhead) or a movable chuck is provided
Data Source
AI summary
An etching device and an etching method. The etching device includes an etching chamber and a chuck located therein for clamping a substrate to be etched, a plasma generating device surrounding the etching chamber in an area and a gas nozzle distribution device for introducing etching gas, which is situated above the chuck in such a way that an etching gas stream is directed essentially perpendicular to a surface of the substrate to be etched. A moving mechanism may be used to change the distance between the gas nozzle distribution device and the chuck as a function of the etching mode.