MEMS Thermal Actuator Oxide Density Control
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Solution Overview
Problem
The manufacturing of MEMS devices using bonded SOI substrates often results in high-density precipitated oxide formation in the silicon layer, leading to dislocation and plastic deformation of thermal actuators, which degrades the operation reliability of the devices, especially when used for extended periods.
Innovation Solution
A MEMS device manufacturing method involving thermal treatment at a temperature where the diffusion flow rate of interstitial silicon atoms exceeds that of interstitial oxygen atoms, followed by processing to suppress precipitated oxide density, ensuring it remains equal to or less than 5×10^5/cm², thereby reducing dislocation occurrence and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bonded SOI substrates manufactured using CZ method are used for MEMS device production, then manufacturing cost is reduced, but precipitated oxide forms at high density in the silicon layer leading to dislocation and plastic deformation
Solution Approach 1:
The patent applies preliminary thermal treatment to the silicon layer before manufacturing the MEMS device. This preliminary action suppresses the formation of precipitated oxide by controlling the diffusion of interstitial atoms, preventing dislocation and plastic deformation before they can occur during device operation, thus maintaining reliability while using cost-effective CZ substrates
Solution Approach 2:
The patent changes the thermal treatment parameters (temperature, time, atmosphere) to control the diffusion flow rate of interstitial silicon and oxygen atoms. By optimizing these parameters, the precipitated oxide density is reduced to 5×10^5/cm² or less, preventing dislocation while maintaining compatibility with standard CZ substrate manufacturing processes
2Reliability
If thermal treatment is performed at high temperature to reduce precipitated oxide density, then dislocation occurrence is suppressed, but manufacturing process complexity increases
Solution Approach 1:
The patent merges the thermal treatment step with existing manufacturing processes such as oxidation or annealing steps already present in the fabrication flow. By combining multiple functions into a single thermal treatment step, the process complexity is minimized while still achieving the required precipitated oxide density reduction
Solution Approach 2:
The patent optimizes thermal treatment parameters to achieve effective precipitated oxide suppression at commercially viable temperatures and durations. The treatment conditions are carefully controlled to balance reliability improvement with manufacturing efficiency, avoiding excessively complex or time-consuming processes
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 effectively reduces dislocation and plastic deformation in thermal actuators, thereby enhancing the operation reliability of MEMS devices and shutter apparatuses by controlling thermal treatment conditions to manage precipitated oxide density.
Implementation Method 1
thermal treatment step of thermally treating a substrate having a silicon layer at a first temperature that the diffusion flow rate of an interstitial silicon atom in a silicon single crystal is higher than the diffusion flow rate of an interstitial oxygen atom
Implementation Method 2
thermal treatment step of thermally treating a substrate having a silicon layer
Implementation Method 3
thermal actuator coupled to the fixing portion and configured to generate heat by current application to displace in a predetermined direction according to a generated heat temperature
Data Source
AI summary
Provided is a method including at least the thermal treatment step of thermally treating a SOI substrate having a first silicon layer at a first temperature that the diffusion flow rate of an interstitial silicon atom in a silicon single crystal is higher than the diffusion flow rate of an interstitial oxygen atom and the processing step of processing the SOI substrate after the thermal treatment step to obtain a displacement enlarging mechanism.