MEMS Cavity Etching with Variable Trench Depths
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Solution Overview
Problem
Existing manufacturing processes for microelectromechanical system (MEMS) structures are not entirely satisfactory as device scaling-down continues, particularly due to inadequate control over etching processes that result in suboptimal yield and performance.
Innovation Solution
The method involves adjusting etching processes to account for the loading effect by using specific etching gases and power settings to form MEMS structures with varying widths, including a main etching process and an over-etching process with distinct steps to control etching rates and prevent over-etching, thereby improving yield and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing manufacturing processes are used for MEMS structures, then general adequacy for intended purposes is achieved, but yield and performance are suboptimal due to inadequate control over etching processes
Solution Approach 1:
The etching process is divided into multiple distinct steps (main etching process, over-etching process, and cleaning process) with different parameters and objectives. Each step targets specific regions or functions, allowing precise control over the etching rate and depth for different structures within the MEMS device.
Solution Approach 2:
The patent employs dynamic adjustment of etching parameters including gas flow rates, power settings, and pressure conditions during different process steps. The etching rate is dynamically controlled to account for loading effects, where wider openings etch faster than narrower ones, requiring real-time parameter optimization.
2Length of moving object
If device scaling-down continues, then miniaturization is achieved, but existing manufacturing processes become inadequate
Solution Approach 1:
Different etching parameters and process conditions are applied to different regions of the substrate based on local requirements. Wider openings receive different etching treatment compared to narrower openings, with customized gas flows and power settings optimized for each opening size to maintain precision during scaling.
Solution Approach 2:
The patent systematically changes multiple process parameters including RF power, gas flow rates, and pressure to optimize etching performance at different device scales. These parameter adjustments compensate for loading effects and maintain consistent etching quality across varying feature sizes.
3Device complexity
If etching processes are not adjusted for loading effect, then process simplicity is maintained, but yield is reduced
Solution Approach 1:
The process includes preliminary steps to prepare the substrate and pattern layers before etching, with specific attention to ensuring uniform thickness and proper alignment. Over-etching steps are planned in advance to compensate for variations in etching rate across different opening widths, preventing yield loss.
Solution Approach 2:
The multi-step etching process incorporates feedback mechanisms where process parameters are adjusted based on observed etching rates and loading effects. The over-etching step serves as a feedback-driven compensation mechanism to ensure complete penetration through varying thicknesses while maintaining control over final dimensions.
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 enhances the yield of MEMS structures by more than 50% and improves their performance by carefully managing etching rates and preventing damage during the manufacturing process.
Implementation Method 1
etching a MEMS substrate to form a number of openings in the MEMS substrate
Implementation Method 2
depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate
Data Source
AI summary
Methods for manufacturing MEMS structures are provided. The method for manufacturing a microelectromechanical system (MEMS) structure includes etching a MEMS substrate to form a first trench and a second trench and etching the MEMS substrate through the first trench and the second trench to form a first through hole and an extended second trench. The method for manufacturing a MEMS structure further includes etching the MEMS substrate through the extended second trench to form a second through hole. In addition, a height of the first trench is greater than ¾ of a height of the MEMS substrate, and a height of the second trench is smaller than ⅔ of the height of the MEMS substrate.