Bypass Structure for MEMS Charge Dissipation

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Solution Overview

Problem

Existing CMOS-MEMS integration techniques face challenges in preventing charge accumulation during the etching process, which can damage integrated circuit devices due to the interconnected nature of MEMS and CMOS devices, leading to issues like device drift, circuit leakage, and reduced reliability.

Innovation Solution

Incorporating a bypass structure that utilizes a doped region with a lower pass-through voltage to discharge etching-induced charge, isolating it from the MEMS device to prevent damage to the CMOS substrate, and optionally disconnecting this structure after packaging to minimize its impact on device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MEMS device is processed last and interconnected to integrated circuit device before etching, then device integration and performance are improved, but charge accumulation during etching damages the integrated circuit device

Engineering Contradiction:

Improvedevice reliabilityVSAvoidetching-induced charge damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A bypass structure is introduced as an intermediary element between the MEMS device and the integrated circuit device. This bypass structure provides a dedicated charge dissipation path that mediates the harmful interaction during etching, allowing charge to be safely discharged without damaging the interconnected circuit devices.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interconnect structure is segmented into functional portions: a first portion interconnected to the integrated circuit device, a second portion forming the bypass structure, and a third portion interconnected to the MEMS device. This segmentation allows the bypass portion to handle charge dissipation separately from the signal transmission paths.

Inventive Principle:

Principle #1Segmentation

2Reliability

If protection diodes are added to prevent charge damage, then device reliability is improved, but device area increases

Engineering Contradiction:

Improvedevice reliabilityVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The bypass structure is merged with the existing interconnect layers and routing of the CMOS-MEMS device. By utilizing the existing multilayer interconnect structure, the charge dissipation function is integrated into the device architecture without requiring additional dedicated space for separate protection components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bypass structure serves multiple functions: it provides charge dissipation during etching, maintains electrical connectivity between MEMS and CMOS components, and can be integrated into existing interconnect layers. This multi-functionality eliminates the need for separate protection diodes that would consume additional area.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If higher power plasma etching is used to improve etching performance, then manufacturing productivity is improved, but charge accumulation and device damage increase

Engineering Contradiction:

Improveetching speedVSAvoidcharge accumulation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The bypass structure converts the harmful effect of charge accumulation into a beneficial process by providing a controlled dissipation path. The increased charge generation from higher power plasma etching is redirected through the bypass structure, transforming what would be damaging charge accumulation into a manageable current flow that protects the device while enabling faster etching.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 bypass structure effectively reduces etching-induced damage, minimizes the area required for protection diodes, enhances the etching process window, and improves the tolerance of CMOS-MEMS devices to higher power plasma environments, thereby improving device reliability and sensitivity.

Implementation Method 1

Incorporating a bypass structure that utilizes a doped region with a lower pass-through voltage to discharge etching-induced charge

Methodology Applied

Scientific EffectCharge discharge through doped region: Conduction (electrical)

Implementation Method 2

etching the second substrate to form a MEMS device... any charge induced by the etching

Methodology Applied

Scientific EffectPlasma etching: Plasma

Data Source

PatentUS8878312B2Electrical bypass structure for MEMS device

Publication Date: 2014.11.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An apparatus including a bypass structure for complementary metal-oxide-semiconductor (CMOS) and/or microelectromechanical system (MEMS) devices, and method for fabricating such apparatus, is disclosed. An exemplary apparatus includes a first substrate; a second substrate that includes a MEMS device; an insulator disposed between the first substrate and the second substrate; and an electrical bypass structure disposed in the insulator layer that contacts a portion of the first substrate, wherein the electrical bypass structure is electrically isolated from the MEMS device in the second substrate and any device included in the first substrate.