CMOS-Compatible MEMS Fabrication Using Copper Metal Layers

Solution Overview

Problem

Current MEMS device fabrication techniques using poly silicon are complex and not compatible with CMOS processes, making it challenging to integrate MEMS devices with semiconductor integrated circuit dies.

Innovation Solution

A semiconductor device is fabricated with a MEMS device constructed above a MOS transistor, featuring a bottom electrode in a second topmost metal layer, a diaphragm in a pad metal layer, and a cavity between the two, using CMOS-compatible processes, allowing for the integration of MEMS devices like microphones or pressure sensors directly on a semiconductor substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polysilicon-based MEMS fabrication techniques are used, then mechanical, electrical, and thermal properties are improved, but process complexity increases and CMOS compatibility is lost

Engineering Contradiction:

Improvemechanical, electrical, and thermal propertiesVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the material parameter from polysilicon to copper, which fundamentally alters the fabrication approach. Copper allows for simpler CMOS-compatible processes while maintaining the necessary electrical and mechanical properties through different material characteristics and deposition techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical polysilicon structure with an electrical-conductive copper structure that achieves the same functional goals through different physical mechanisms, enabling compatibility with standard CMOS electrical processing while maintaining device performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If polysilicon-based MEMS fabrication techniques are used, then mechanical, electrical, and thermal properties are improved, but CMOS compatibility deteriorates

Engineering Contradiction:

Improvemechanical, electrical, and thermal propertiesVSAvoidCMOS process compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameter from polysilicon to copper, which fundamentally alters the fabrication approach. Copper allows for simpler CMOS-compatible processes while maintaining the necessary electrical and mechanical properties through different material characteristics and deposition techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent makes the MEMS fabrication process universal by using copper, a material that can be processed through standard CMOS fabrication lines. This enables the same manufacturing infrastructure to produce both traditional semiconductor devices and MEMS devices with integrated sensors, achieving multi-functionality in the fabrication system

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If MEMS devices are integrated with semiconductor integrated circuit dies, then device functionality is improved, but fabrication complexity increases

Engineering Contradiction:

Improveintegration capabilityVSAvoidfabrication process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges MEMS device fabrication with standard CMOS semiconductor manufacturing processes by using copper as a common material. This integration allows both the semiconductor circuit and MEMS sensor to be fabricated simultaneously in the same fabrication line, reducing overall process complexity despite the enhanced functionality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the material parameter from polysilicon to copper, which fundamentally alters the fabrication approach. Copper allows for simpler CMOS-compatible processes while maintaining the necessary electrical and mechanical properties through different material characteristics and deposition techniques

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10640372B2Method for fabricating MEMS device integrated with a semiconductor integrated circuit

Publication Date: 2020.05.05 MARLIN SEMICON LTD

AI summary

A method for fabricating a semiconductor device is disclosed. A semiconductor substrate comprising a MOS transistor is provided. A MEMS device is formed over the MOS transistor. The MEMS device includes a bottom electrode in a second topmost metal layer, a diaphragm in a pad metal layer, and a cavity between the bottom electrode and the diaphragm.