Texas Instruments Corporation

Mark L Jenson

Mona M Eissa

Sudtida Lavangkul

Sopa Chevacharoenkul

Mark R Kimmich

Yousong Zhang

Byron J R Shulver

Lee Alan Stringer

An integrated circuit has a substrate, a circuit, a core structure, a first encapsulation layer, a second encapsulation layer, and an oxide layer. The circuit includes transistors with active regions developed on the substrate and a metal layer formed above the active regions to provide interconnections for the transistors. The core structure is formed above the metal layer. The first encapsulation layer covers the core structure, and it has a first thermal expansion coefficient. The second encapsulation layer covers the first encapsulation layer over the core structure, and it has a second thermal expansion coefficient that is different from the first thermal expansion coefficient. As a part of the stress relief structure, the oxide layer is formed above the second encapsulation layer. The oxide layer includes an oxide thickness sufficient to mitigate a thermal stress between the first and second encapsulation layers.

Integrated fluxgate device

An etchant for simultaneously etching NiFe and AlN with approximately equal etch rates that comprises phosphoric acid, acetic acid, nitric acid and deionized water. Alternating layers of NiFe and AlN may be used to form a magnetic core of a fluxgate magnetometer in an integrated circuit. The wet etch provides a good etch rate of the alternating layers with good dimensional control and with a good resulting magnetic core profile. The alternating layers of NiFe and AlN may be encapsulated with a stress relief layer. A resist pattern may be used to define the magnetic core geometry. The overetch time of the wet etch may be controlled so that the magnetic core pattern extends at least 1.5 um beyond the base of the magnetic core post etch. The photo mask used to form the resist pattern may also be used to form a stress relief etch pattern.

Process for NiFe fluxgate device

A method comprises forming an etch stop layer, a first titanium layer, a magnetic core, a second titanium layer, and patterning the first and second titanium layers. The etch stop layer is formed above a substrate. The first titanium layer is formed on the etch stop layer. The magnetic core is formed on the first titanium layer. The second titanium layer has a first portion encapsulating the magnetic core with the first titanium layer, and a second portion interfacing with the first titanium layer beyond the magnetic core. The patterning of the first and second titanium layers includes forming a mask over a magnetic core region and etching the first and second titanium layers exposed by the mask using a titanium etchant and a titanium oxide etchant.

Selective patterning of titanium encapsulation layers

Selective patterning of an integrated fluxgate device

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Allen, TX, United States of America

Mark L Jenson