P. Böttger16 November 2017

SEMICON EuropaMunich, Germany

Ion Beam Etching Technologies for Sensor Manufacturing

2Ion Beam Etching Technologies for Sensor Manufacturing

Provide vacuum processing equipment for MEMS/sensor and optics industry

Coating

Etching/structuring

Special/customised equipment

Founded in 2013

Located in Chemnitz

(300 km north of Munich)

Private company with 50.1 % shares

of VON ARDENNE GmbH, Dresden

Ca. 100 employees

20 … 30 Mio. EUR annual revenue

scia Systems Company

Aerial photograph of Technologie Centrum Chemnitz (TCC)

3Ion Beam Etching Technologies for Sensor Manufacturing

Technological Background

Principles of ion beam etching

4Ion Beam Etching Technologies for Sensor Manufacturing

Ion Beam Etching Principles

Atoms of target material can be ejected by bombardment of high-energy ions

Momentum exchange between incident ions and atoms of the target material in

collision cascades

Material removal with Angstrom accuracy (Ion Beam Etching)

Implantation of ions (Ion Implantation)

Any material with a sufficient high melting point can be etched

Low process pressure (10-4 mbar) and temperature (< 100 °C)

Process with resolution

on atomic scale

5Ion Beam Etching Technologies for Sensor Manufacturing

Basic components of ion beam milling arrangement

Ion Beam Milling Principles

Generation of ion beam by broad

beam ion source

Ionization of process gas by electric

discharge (RF or DC)

Multi aperture extraction grid systems

for ion extraction and beam shape

formation

Separate electron neutralizer for ion

charge neutralization

High vacuum conditions for sufficient

ion mean free path larger than

substrate distance

Substrate sage for positioning and

cooling of substrate

6Ion Beam Etching Technologies for Sensor Manufacturing

scia Mill 150

Ion beam milling for

wafers up to 150 mm or

irregular samples

Flexible tool for R&D and

small scale production

Ion Beam Etching Equipment

scia Mill 200

Ion beam milling for

wafers up to 200 mm

Production tool meeting

industry standards,

cluster compatible

scia Coat 200

Upgrade to dual ion

beam deposition for

wafers up to 200 mm or

irregular samples

R&D or production layout

in cluster configuration

> 15 ion beam etching chambers shipped or in order backlog since 2014

7Ion Beam Etching Technologies for Sensor Manufacturing

scia Mill 200 - Process Arrangement

Substrate Holder

200 mm

Ion Beam Source

RF350-e

Argon

50 … 600 eV

800 mA

8Ion Beam Etching Technologies for Sensor Manufacturing

scia Coat 200 - Process Arrangement

Substrate Holder

200 mm

Assist Ion Source

RF350-e

Argon, Oxygen

50 … 600 eV

800 mA

Sputter

Ion Source

RF120-e

Argon

600 … 1800 eV

400 mA

Target Drum

4 or 6 Materials

9Ion Beam Etching Technologies for Sensor Manufacturing

Application

Structuring of Spintronic Sensors

10Ion Beam Etching Technologies for Sensor Manufacturing

Principle of MTJ-based Sensors

Use of electron‘s spin-degree in magnetic sensors

based on magnetic tunnel junctions (MTJ)

Thin non-magnetic, insulating tunnel barrier layer

sandwiched in between two ferromagnetic (FM) layers

Upper FM layer’s magnetization easily changeable by

applying an external magnetic field (free FM layer)

Lower FM layer‘s magnetization pinned by antiferro-

magnetic (AFM) layer below (pinned FM layer)

Relative magnetic orientation of both FM layers

defines electric resistivity of tunnel barrier layer

Magnitude of tunnel magnetoresistance (TMR)

expressed by ratio:

Schematic of a magnetic tunnel

junction (MTJ)

Low TMR High TMR

P

PAP

R

RR

R

R

RAP and RP are the respective resistances for the antiparallel (AP) and parallel (P) magnetic states

11Ion Beam Etching Technologies for Sensor Manufacturing

Deposition of Sensor Layer Stack

Layers of magnetic stack are deposited by

magnetron sputtering

Silicon substrate with silicon oxide on top

Ta (5 nm) / Ru (30 nm) / Ta (10 nm) /

Ru (10 nm) / MnIr (20 nm) / CoFe (3 nm) /

Ru (0.8 nm) / CoFeB (3 nm) /

MgO (1.7 nm) / CoFeB (3 nm) / Ta (5 nm) /

Ru (5 nm)

Annealing at 360 °C for 60 min in an external

field of ~ 5500 Oe, to induce pinning and

crystallize the MgO layer

Patterned by masks made of positive

photoresist for formation of upper contacts

Layer stack with hard mask

High resolution TEM cross section of a standard MTJ

12Ion Beam Etching Technologies for Sensor Manufacturing

Sensor Structuring using Ion Beam Etching

Removing of unmasked material by ion beam etching with argon as process gas

In situ deposition of insulating encapsulation using DIBD

Process controlled by Secondary Ion Mass Spectrometer (SIMS), to detect layer boundaries and determine angle change points and etch stops

SIMS is sensitive to layer thick-nesses in the single-digit nm range

Stack was etched at 30° down to the 10 nm Ta layer, all materials were detected by the SIMS

Creation of MTJs by ion beam etching

SIMS signal for different materials in layer stack

13Ion Beam Etching Technologies for Sensor Manufacturing

TMR Evaluation

TMR plotted versus the applied magnetic field

TMR value reaches 140 %

High value indicates lack of critical sidewall deposition

TMR versus applied magnetic field

Selecting a high enough field range, enables to switch the exchange biased

pinned layer and the free layer (left)

In a reduced field range, only the pinned layer changes its magnetization

(right)

14Ion Beam Etching Technologies for Sensor Manufacturing

Summary

Ion beam etching most suitable for structuring of multi-layered sensor stacks

Exact process control with SIMS down to single nm range

Prevention of side wall redeposition during etching by use of angled ion beam

incidence

In situ deposition of adhesion, intermediate or capping layers possible using

dual ion beam deposition process arrangement

scia Systems GmbH

Annaberger Straße 240

09125 Chemnitz

Germany

Phone: +49 371 5347-780

Fax: +49 371 5347-781

info@scia-systems.com

www.scia-systems.com

Chemnitz

Dresden

Thank you for your attention!