MEMS Actuator Layer Transfer Using Reusable Carrier Wafers

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Solution Overview

Problem

Conventional methods for forming MEMS actuator layers require thermal budgeting and release holes, which impact circuitry and increase fabrication costs by consuming wafers.

Innovation Solution

A method involving a reusable carrier wafer process where a dielectric and cleave layer are deposited on a carrier wafer, followed by separation to form a handle wafer and a reusable carrier wafer, eliminating the need for release holes and thermal budgeting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If silicon or poly-silicon is deposited on a substrate to form an actuator layer, then the actuator layer can be created, but release holes must be placed in the proof mass and thermal budgeting is required which adversely impacts circuitry

Engineering Contradiction:

Improveactuator layer formationVSAvoidthermal impact on circuitry and release hole requirements

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent segments the fabrication process into distinct stages: forming the actuator layer on a first substrate, bonding a handle wafer to it, and then separating them. This segmentation allows the actuator layer to be created without direct thermal exposure to the final device structure, eliminating the need for release holes and reducing thermal impact on sensitive circuitry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The actuator layer is formed in advance on a sacrificial substrate before the final device assembly. This preliminary action allows the layer to be created under optimized conditions without concern for thermal budgeting in the final device, as the substrate will be removed later through the handle wafer bonding and separation process.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If a wafer is thinned after the fusion bond process to eliminate release holes and thermal budgeting, then the actuator layer can be formed without those constraints, but the wafer is consumed and fabrication cost increases

Engineering Contradiction:

Improveactuator layer formation without release holesVSAvoidwafer consumption

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent introduces a handle wafer as an intermediary element that enables the actuator layer to be formed on a reusable substrate. The handle wafer is bonded to the substrate containing the actuator layer, and then the original substrate is removed through separation. This intermediary approach allows the substrate to be reused rather than consumed, eliminating fabrication costs associated with wafer loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The original substrate serving as a sacrificial carrier is discarded after serving its purpose of supporting actuator layer formation. However, the process is designed so that the handle wafer and actuator layer are recovered and can be used in subsequent fabrication steps, effectively recovering the valuable components while disposing of only the inexpensive carrier substrate.

Inventive Principle:

Principle #34Discarding and recovering

3Ease of manufacture

If release holes are formed in the proof mass to create the actuator layer, then the layer can be formed, but the device complexity and fabrication steps increase

Engineering Contradiction:

Improveactuator layer creationVSAvoidfabrication process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

Instead of forming release holes in the final device structure to create the actuator layer, the patent inverts the approach by forming the actuator layer on a separate substrate first, then bonding that substrate to the handle wafer. This inversion eliminates the need for complex release hole formation steps in the proof mass, simplifying the overall fabrication process.

Inventive Principle:

Principle #13The other way round (Inversion)

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

Reduces fabrication costs and eliminates the need for thermal budgeting considerations while maintaining the integrity of the MEMS device, allowing for cost-effective and efficient production of MEMS actuator layers.

Implementation Method 1

the separating includes shining an infrared light onto the handle wafer and the carrier wafer after the Si layer is coupled to the handle wafer... shining a visible light onto the handle wafer and the carrier wafer after the Si layer is coupled to the handle wafer, wherein the shining weakens the cleave layer

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS20250304434A1Actuator layer deposition and transfer

Publication Date: 2025.10.02 INVENSENSE INC

AI summary

A method includes forming a dielectric layer on a carrier wafer with a top surface and a bottom surface, wherein the top surface is positioned opposite to the bottom surface. The method includes forming a cleave layer on the dielectric layer that covers the top surface of the carrier wafer. Method includes forming a silicon Oxide layer (SiO2) over the cleave layer and coupling the Si layer to a handle wafer, wherein the handle wafer comprises silicon and wherein the handle wafer includes at least one cavity, wherein the Si layer encloses the at least one cavity. The method includes separating the carrier wafer from the handle wafer, wherein the separating forms a first wafer and a second wafer, wherein the first wafer comprises the handle wafer and the Si layer and a portion of the cleave layer, and wherein the second wafer is a reusable carrier wafer.