Capacitive Pressure Sensor Membrane Sealing for Buried Cavity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing MEMS devices, particularly capacitive pressure sensors, face challenges in completely filling etching holes due to the use of conformal or non-conformal materials, leading to false capacitive coupling or incomplete sealing, which compromises the integrity and functionality of the membrane.
Innovation Solution
A method involving the use of a sacrificial layer with a combination of etch stop layers and a permeable polysilicon layer to form a buried cavity, allowing precise control over membrane formation and sealing, using crystallized aluminum oxide and amorphous silicon to ensure accurate membrane size and pressure regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conformal material is used to fill etching holes, then complete filling is achieved, but the material penetrates into the cavity and causes false capacitive coupling
Solution Approach 1:
A plug layer is introduced as an intermediary material between the conformal filling material and the cavity. This plug layer has a gradient structure with different dielectric constants, allowing the conformal material to fill the holes completely while preventing it from penetrating into the cavity and causing false capacitive coupling. The gradient structure provides a transition zone that blocks the harmful penetration.
2Object-generated harmful factors
If non-conformal material is used to fill etching holes, then false capacitive coupling is prevented, but the holes are not completely filled
Solution Approach 1:
The filling structure uses a composite of two materials: a non-conformal material that prevents false capacitive coupling by not penetrating into the cavity, and a conformal material that provides complete filling. The non-conformal material forms the primary filling that stops before the cavity, while the conformal material fills the remaining space without causing harmful coupling.
3Object-generated harmful factors
If two different materials are used (first non-conformal to narrow opening, second conformal to fill), then false capacitive coupling is prevented, but the process complexity increases
Solution Approach 1:
The filling process is segmented into distinct stages: first forming the plug layer with gradient structure to prevent penetration, then filling the remaining space with conformal material. This segmentation allows each material to perform its specific function optimally while maintaining a manageable manufacturing process through clear process steps.
4Length of moving object
If etching holes are made narrow and deep for thick membrane applications, then membrane thickness is increased, but complete filling becomes more difficult
Solution Approach 1:
The physical and chemical parameters of the filling materials are optimized for narrow and deep holes. The plug layer material has specific viscosity and curing characteristics that allow it to be deposited in thin layers that can flow into and fill deep, narrow holes uniformly. The gradient structure parameters are tuned to ensure proper penetration depth without over-filling into the cavity.
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 enables robust and accurate production of MEMS devices with reliable membranes, reducing the risk of breakage and deformation, ensuring high yield and cost-effectiveness, while allowing for precise membrane thickness and shape control.
Implementation Method 1
removing the sacrificial portion (8') through the first membrane layer (20) using said etching chemical solution
Implementation Method 2
forming, on said sacrificial portion (8'), a first membrane layer (20) of a porous material, which is permeable to said etching chemical solution
Implementation Method 3
forming, on the first protection layer (5), a sacrificial layer (8, 8') of a material that may be removed through said etching chemical solution; forming, on the sacrificial layer (8, 8'), a second protection layer (15) impermeable to said etching chemical solution
Implementation Method 4
using crystallized aluminum oxide and amorphous silicon to ensure accurate membrane size and pressure regulation
Implementation Method 5
this membrane represents a variable electrode, facing a fixed portion forming a fixed electrode and separated therefrom by a partially or totally buried cavity
Data Source
AI summary
The present disclosure is directed to a method for manufacturing a micro-electro-mechanical device. The method includes the steps of forming, on a substrate, a first protection layer of crystallized aluminum oxide, impermeable to HF; forming, on the first protection layer, a sacrificial layer of silicon oxide removable with HF; forming, on the sacrificial layer, a second protection layer of crystallized aluminum oxide; exposing a sacrificial portion of the sacrificial layer; forming, on the sacrificial portion, a first membrane layer of a porous material, permeable to HF; forming a cavity by removing the sacrificial portion through the first membrane layer; and sealing pores of the first membrane layer by forming a second membrane layer on the first membrane layer.