MEMS Structure Deflection for Non-Destructive Under-Etch Testing

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Solution Overview

Problem

Current methods for measuring under-etching in semiconductor technology are either destructive or time-consuming, and unable to generate large amounts of data quickly, limiting their effectiveness in controlling under-etching in MEMS devices.

Innovation Solution

A method involving a mechanical force applied perpendicular to a structure above a substrate, with a sacrificial layer, to determine the presence and position of the sacrificial layer through deflection measurement, allowing for non-destructive and efficient assessment of under-etching without damaging the structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If cross-section scanning electron microscopy (XSEM) is used to measure under-etched distance, then measurement accuracy is improved, but sample preparation becomes tedious and time-consuming

Engineering Contradiction:

Improveunder-etched distance measurement accuracyVSAvoidsample preparation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The invention extracts the measurement function from destructive cross-section imaging and implements it through non-destructive top-view imaging combined with mechanical deflection measurement. The deflection measurement system separates the measurement process from sample preparation requirements, allowing direct measurement without cleavage or sectioning.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces the optical/electronic measurement system (XSEM) with a mechanical measurement system that applies force to the structural layer and measures deflection. This mechanical approach provides sufficient measurement precision without requiring the complex sample preparation needed for XSEM.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Difficulty of detecting and measuring

If the top layer is removed to enable top view imaging, then measurement capability is improved, but the measurement becomes destructive

Engineering Contradiction:

Improveunder-etch visibilityVSAvoidsample integrity

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The invention introduces mechanical deflection measurement as an intermediary method that bridges the gap between needing to see the under-etch and maintaining sample integrity. Instead of directly imaging the under-etched area (which requires removing the top layer), the system measures the mechanical response of the top layer to infer the under-etch condition, preserving the sample while enabling measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If conventional measurement methods are used, then measurement capability is achieved, but productivity is reduced due to time-consuming processes

Engineering Contradiction:

Improveunder-etch determination capabilityVSAvoidmeasurement throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The invention segments the measurement approach by using an array of test structures with different geometries (beams, plates, holes) that can be measured independently through parallel deflection measurements. This segmentation allows multiple measurements to be performed efficiently, improving productivity while maintaining precision for each individual structure type.

Inventive Principle:

Principle #1Segmentation

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 rapid, non-destructive determination of under-etch distance and etching conditions, improving the control of under-etching in MEMS devices by correlating deflection with the presence of the sacrificial layer, thus enhancing the efficiency of the MEMS production process.

Implementation Method 1

exerting a force, for example a mechanical force, on the at least one structure, the force having a predetermined amplitude and having a component perpendicular to the substrate

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Implementation Method 2

determining the deflection of the structure perpendicular to the plane of the substrate, and correlating the deflection of the structure to the presence of a sacrificial layer

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP2202197B1Method for testing MEMS devices

Publication Date: 2014.03.05 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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Figure 2a
Figure 2b

AI summary

A method for determining the presence of a sacrificial layer (41c, 41d, 41e) under a structure (40a, 40b, 40c, 40d, 40e) comprises: providing at least one structure (40a, 40b, 40c, 40d, 40e) arranged above a substrate having a major surface lying in a plane, the at least one structure (40a, 40b, 40c, 40d, 40e) being clamped at at least one side, exerting a force, for example mechanical force, on the at least one structure (40a, 40b, 40c, 40d, 40e), the force, for example mechanical force, having a predetermined amplitude and having a component perpendicular to the substrate, determining the deflection of the at least one structure (40a, 40b, 40c, 40d, 40e) perpendicular to the plane of the substrate, and correlating the deflection of the at least one structure (40a, 40b, 40c, 40d, 40e) to the presence of a sacrificial layer (41c, 41d, 41e) between the substrate and the structure (40a, 40b, 40c, 40d, 40e).