Product Embedded Surface Sensors Integrated Under Wear ...
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Product Embedded Surface Sensors Integrated Under Wear Resistant Coatings Introduction The industry is continuously demanding more actively responding machine parts capable of communicating their current state of operation. Today you can buy many different types of discrete thin film sensors off the shelf, but many environments cannot tolerate insertion of discrete components. With surface embedded sensors under wear resistant coatings we can create intelligent machine parts with active-adaptive protection through online control of the current physical status. The fabrication of surface embedded sensors on three- dimensional (3D) machine parts and other high-tech products require new technologically demanding approaches. The present trans-Nordic COSMOS project has successfully merged clean room based sensor design and fabrication with wear-resistant hard coatings, fabricating a prototype of a surface embedded temperature sensor on a steel substrate. Insulating Layer For standard clean room processed structures it would be straight forward to either grow a thermal silicon oxide or deposit an insulating layer by PECVD or LPCVD to get a good electrical isolation between the sensor structure and the substrate. Since the substrates relevant for the COSMOS project have geometries far beyond flat silicon wafers and in some cases also have a limited process temperature window, these techniques cannot be used. Instead we have been investigating other deposition techniques such as DC Sputtering, Magnetron Sputtering, Arc Diamond Like Carbon (Arc-DLC), Ion Beam Assisted Deposition of DLC (IBAD- DLC) and Atomic Layer Deposition (ALD). Sensor Fabrication Thin film sensors are traditionally fabricated by deposition of metal and isolation layers with subtractive or additive patterning by conventional photolithography and clean room processing techniques. However, these processes require flat and smooth surfaces which is not valid for industrially machined parts. Therefore our sensor structures were fabricated using shadow mask technology where the sensor materials are directly patterned during deposition through a plate with openings, e.g. a patterned metal foil. We used a magnetic metal called 7C27Mo2 with openings down to 100 μm in size. The shadow mask was held in place using several strong magnets on the back side of the substrate. y [ohm] = 0,74 * Temp + 511,4 R2 = 0,99 500 525 550 575 600 625 650 0 50 100 150 200 Temperature (C) resistance / ohm Acknowledgements We want to thank the Nordic Innovation Center, NICe, for the financial support. Tommy Schönberg 1 , Magnus Svensson 1 , Lars Pleth Nielsen 2 , Helena Ronkainen 3 , Niels Peter Østbø 4 1 Acreo AB (Sweden), 2 DTI (Denmark), 3 VTT (Finland), 4 SINTEF ICT (Norway) COSMOS Components and Smart Machines with Micro-Nano Surface Embedded Sensors Substrate AlN Cu Substrate AlN Cu Steel Chromia Alumina Chromia or CrN Alumina Alumina Alumina Chromia Chromia Chromia Steel Chromia Alumina Chromia or CrN Alumina Alumina Alumina Chromia Chromia Chromia In the cases of DLC coatings it was necessary to increase the adhesion of the sensor layer to the underlying DLC-layer by pre-treating the substrate with 70 keV oxygen implantation. The best results for the isolating layer were obtained for multilayer insulating coating system such as: (i) an Atomic Layer Deposition of Al 2 O 3 followed by Dual Magnetron Deposition of Al 2 O 3 , or (ii) several layers of Diamond Like Carbon (DLC, Ta:C), or (iii) a multilayer system composed of several layers of alternating Al 2 O 3 / Cr 2 O 3 . Temperature Measurement A prototype Pt100-like temperature sensor was buried under Diamond Like Carbon revealing promising properties for a wide range of industrial applications. The resistive sensor response gives a close to linear signal as a function of the temperature. Close-up image of the sensor structures revealing the fingerprint of the underlying Pt structures Temperature response for a surface embedded sensor sandwiched between multilayer Cr 2 O 3 / Al 2 O 3 and a non-conducting IBAD DLC coating. Several different types of sensor structures were fabricated on a steel substrate using a shadow mask. A 1000 Å thick Pt layer with an underlying adhesion layer of 50 Å Ti was deposited using E-beam evaporation. Substrate CrN-CrC DLC Embedded sensor There are several difficulties that need to be addressed and subsequently overcome in order to fabricate a working sensor on a traditionally 3D machined metal part. First the metal needs to be electrically isolated, second, the sensor structure needs to be fabricated on the surface and third, the sensor needs to be embedded under a wear resistant coating to protect it from mechanical damage. The coatings were tested on several different parameters. Here we see the results from a 150 kg Rockwell C indentation of a buried sensor under DLC. No delamination of the coating means good adhesion and pass on the test. The 100 μm thin shadow mask is formed as a 4” wafer to fit the processing equipment without any need for special holders. The industrial steel substrates are 100 mm in diameter for the same reason. AlN was one of the tested coatings that showed poor insulating qualities. This could be due to pin holes in the coating or in poor step coverage of the rough substrate surface. Al 2 O 3 is generally a good insulating material, but the final results are very much dependent of the deposition technique used to cover the substrate. Dual magnetron deposition showed poor insulation, but with an underlying ALD layer of Al 2 O 3 the insulation was perfect. The insulating properties can also be improved by alternating the coating material in several steps and thereby creating a multilayer coating. Here we see a dual magnetron multilayer stack of Al 2 O 3 / Cr 2 O 3 .
Transcript of Product Embedded Surface Sensors Integrated Under Wear ...
Product Embedded Surface Sensors
Integrated Under Wear Resistant Coatings
Introduction
The industry is continuously demanding more actively responding machine parts
capable of communicating their current state of operation. Today you can buy
many different types of discrete thin film sensors off the shelf, but many
environments cannot tolerate insertion of discrete components. With surface
embedded sensors under wear resistant coatings we can create intelligent
machine parts with active-adaptive protection through online control of the
current physical status. The fabrication of surface embedded sensors on three-
dimensional (3D) machine parts and other high-tech products require new
technologically demanding approaches. The present trans-Nordic COSMOS
project has successfully merged clean room based sensor design and fabrication
with wear-resistant hard coatings, fabricating a prototype of a surface embedded
temperature sensor on a steel substrate.
Insulating Layer
For standard clean room processed structures it would be straight forward to either
grow a thermal silicon oxide or deposit an insulating layer by PECVD or LPCVD to
get a good electrical isolation between the sensor structure and the substrate.
Since the substrates relevant for the COSMOS project have geometries far beyond
flat silicon wafers and in some cases also have a limited process temperature
window, these techniques cannot be used. Instead we have been investigating
other deposition techniques such as DC Sputtering, Magnetron Sputtering, Arc
Diamond Like Carbon (Arc-DLC), Ion Beam Assisted Deposition of DLC (IBAD-
DLC) and Atomic Layer Deposition (ALD).
Sensor Fabrication
Thin film sensors are traditionally fabricated by deposition of metal and isolation
layers with subtractive or additive patterning by conventional photolithography
and clean room processing techniques. However, these processes require flat
and smooth surfaces which is not valid for industrially machined parts. Therefore
our sensor structures were fabricated using shadow mask technology where the
sensor materials are directly patterned during deposition through a plate with
openings, e.g. a patterned metal foil. We used a magnetic metal called 7C27Mo2
with openings down to 100 µm in size. The shadow mask was held in place
using several strong magnets on the back side of the substrate.
y [ohm] = 0,74 * Temp + 511,4
R2 = 0,99
500
525
550
575
600
625
650
0 50 100 150 200
Temperature (C)
res
ista
nc
e /
oh
m
AcknowledgementsWe want to thank the Nordic Innovation Center, NICe, for the financial support.
Tommy Schönberg1, Magnus Svensson1, Lars Pleth Nielsen2, Helena Ronkainen3, Niels Peter Østbø4
1Acreo AB (Sweden), 2DTI (Denmark), 3VTT (Finland), 4SINTEF ICT (Norway)
COSMOSComponents and Smart Machines with
Micro-Nano Surface Embedded Sensors
Substrate
AlN
Cu
Substrate
AlN
Cu
Steel
ChromiaAlumina
Chromia or CrN
Alumina
Alumina
Alumina
Chromia
Chromia
Chromia
Steel
ChromiaAlumina
Chromia or CrN
Alumina
Alumina
Alumina
Chromia
Chromia
Chromia
In the cases of DLC coatings it was necessary to increase the adhesion of the sensor layer to the underlying DLC-layer by pre-treating the substrate with 70 keV oxygen implantation.
The best results for the isolating layer were obtained for multilayer insulating
coating system such as: (i) an Atomic Layer Deposition of Al2O3 followed by Dual
Magnetron Deposition of Al2O3, or (ii) several layers of Diamond Like Carbon
(DLC, Ta:C), or (iii) a multilayer system composed of several layers of alternating
Al2O3 / Cr2O3.
Temperature Measurement
A prototype Pt100-like temperature sensor was buried under Diamond Like Carbon
revealing promising properties for a wide range of industrial applications. The
resistive sensor response gives a close to linear signal as a function of the
temperature.
Close-up image of the sensor structures revealing the fingerprint of the underlying Pt structures
Temperature response for a surface embedded sensor sandwiched between multilayer Cr2O3 / Al2O3 and a non-conducting IBAD DLC coating.
Several different types of sensor structures were fabricated on a steel substrate using a shadow mask. A 1000 Å thick Pt layer with an underlying adhesion layer of 50 Å Ti was deposited using E-beam evaporation.
Substrate
CrN-CrC
DLC
Embedded
sensor
There are several difficulties that need to be addressed and subsequently overcome in order to fabricate a working sensor on a traditionally 3D machined metal part. First the metal needs to be electrically isolated, second, the sensor structure needs to be fabricated on the surface and third, the sensor needs to be embedded under a wear resistant coating to protect it from mechanical damage.
The coatings were tested on several different parameters. Here we see the results from a 150 kg Rockwell C indentation of a buried sensor under DLC. No delamination of the coating means good adhesion and pass on the test.
The 100 µm thin shadow mask is formed as a 4” wafer to fit the processing equipment without any need for special holders. The industrial steel substrates are 100 mm in diameter for the same reason.
AlN was one of the tested coatings that showed poor insulating qualities. This could be due to pin holes in the coating or in poor step coverage of the rough substrate surface.
Al2O3 is generally a good insulating material, but the final results are very much dependent of the deposition technique used to cover the substrate. Dual magnetron deposition showed poor insulation, but with an underlying ALD layer of Al2O3 the insulation was perfect.
The insulating properties can also be improved by alternating the coating material in several steps and thereby creating a multilayer coating. Here we see a dual magnetron multilayer stack of Al2O3 / Cr2O3.
