Silicon Timepiece Component Strengthening via Hydrogen Smoothing
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Solution Overview
Problem
Silicon timepiece components are fragile due to their micromachinable nature and deep reactive-ion etching process, which results in rough sidewalls with defects that reduce mechanical strength and increase the risk of breakage under mechanical stress, and existing solutions for strengthening these components either consume silicon or modify their dimensions.
Innovation Solution
A process involving hydrogen smoothing and the formation of a thick oxide layer, with a thickness greater than 1 micron, to enhance the mechanical properties of silicon timepiece components, combining smoothing and oxide layer formation to improve strength without altering the component's dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep reactive-ion etching is used to manufacture silicon timepiece components, then micrometric precision and high production efficiency are achieved, but the sidewalls become rough with defects that reduce mechanical strength
Solution Approach 1:
The patent applies preliminary action by performing hydrogen annealing treatment before the component is subjected to mechanical stress or assembly. This pre-treatment smooths the sidewalls and eliminates defect sites that would otherwise initiate cracks, thereby strengthening the component before it encounters operational stresses.
Solution Approach 2:
The patent changes the physical-chemical parameters of the silicon surface by subjecting it to hydrogen annealing at elevated temperatures (typically 400-900°C). This parameter change transforms the surface morphology from rough with defects to smooth and defect-free, thereby improving mechanical strength without altering the component's dimensions.
2Strength
If existing strengthening solutions (thermal oxidation) are applied to silicon components, then mechanical strength is improved, but silicon is consumed and initial dimensions are modified
Solution Approach 1:
The patent replaces the chemical oxidation process with a physical hydrogen annealing process. Instead of forming silicon oxide that consumes material, hydrogen annealing uses hydrogen gas at elevated temperature to smooth the surface and eliminate defects without consuming silicon or altering dimensions. This substitution maintains manufacturing precision while achieving strengthening.
Solution Approach 2:
The patent changes the temperature and atmospheric parameters during processing by using hydrogen annealing at controlled temperatures (400-900°C) in a hydrogen atmosphere. This parameter change achieves surface smoothing and defect elimination without the material consumption associated with oxidation, thereby preserving the component's initial 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
The process significantly increases the mean and minimum strength at break of silicon timepiece components, reducing the risk of premature breakage, with a mean strength at break of about 5000 MPa and minimum strength above 3000 MPa, effectively addressing the fragility issues while maintaining the initial dimensions.
Implementation Method 1
The migration of silicon is promoted by hydrogen and temperature, and allows sidewall surface defects to be smoothed without consuming silicon
Implementation Method 2
The migration of silicon is promoted by hydrogen and temperature
Implementation Method 3
a formed silicon-oxide layer by thermal oxidation of the silicon at a temperature comprised between 900° C. and 1200° C. The formed oxide layer results from a conversion of the silicon on the surface of the component into silicon oxide
Data Source
AI summary
Timepiece component based on a micromachinable material, including at least one micromachinable-material surface portion that is smoothed at least by hydrogen smoothing. The at least one micromachinable-material surface portion includes an oxide layer of thickness larger than 1 micron in order to increase its mechanical strength. In a particular embodiment the micromachinable material can be silicon and the oxide layer silicon oxide.