MEMS Wafer Shielding During Backside Dicing

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Solution Overview

Problem

Microelectromechanical systems (MEMS) structures are prone to damage and contamination during the wafer dicing process, particularly due to water jet spray and rinsing, which can cause fractures in delicate components like sense diaphragms for pressure sensors.

Innovation Solution

A non-active feature, such as a polyimide or nitride film, is applied to regions on the MEMS wafer devoid of structures, protruding above the plane to prevent contact with dicing tape and protect MEMS structures during the dicing process, even under significant force or pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wafer dicing is performed using conventional methods with water jet spray and rinsing, then the dicing process can be completed efficiently, but the MEMS structures are damaged or contaminated due to water contact and mechanical stress

Engineering Contradiction:

Improvedicing efficiencyVSAvoidMEMS structure integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A protective layer is applied to the MEMS wafer before the dicing process begins. This preliminary protective measure ensures that when water jet spray and rinsing occur during dicing, the water contacts only the protective layer rather than the delicate MEMS structures, preventing damage and contamination while maintaining efficient dicing operations

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective layer serves as an intermediary barrier between the harmful water spray/rinsing and the vulnerable MEMS structures. This intermediate layer absorbs the harmful effects of water contact and mechanical stress during dicing, allowing the dicing process to proceed efficiently while protecting the MEMS integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If water jet spray is used during dicing to cool and rinse the wafer, then the dicing process can proceed smoothly, but the delicate MEMS components like sense diaphragms are fractured or contaminated

Engineering Contradiction:

Improvedicing process smoothnessVSAvoidwater-induced damage to MEMS

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The protective layer is designed to be water-soluble or removable after dicing. The water spray that would normally harm the MEMS structures is instead directed at the protective layer, which safely absorbs the water contact. After dicing completes, the protective layer is removed, having served its protective purpose and converted the harmful water spray into a benign process

Inventive Principle:

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

Data Source

PatentUS9346671B2Shielding MEMS structures during wafer dicing

Publication Date: 2016.05.24 STMICROELECTRONICS INT NV

AI summary

A MEMS wafer (46) includes a front side (52) having a plurality of MEMS structure sites (60) at which MEMS structures (50) are located. A method (40) for protecting the MEMS structures (50) includes applying (44) a non-active feature (66) on the front side of the MEMS wafer in a region that is devoid of the MEMS structures and mounting (76) the front side of the MEMS wafer in a dicing frame (86) such that a back side (74) of the MEMS wafer is exposed. The MEMS wafer is then diced (102) from the back side into a plurality of MEMS dies (48).