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Monolith Semiconductor Inc.
Taking'Silicon'Carbide'Fabless:'Opportunity'and'Challenges'
Kevin'Matocha'President,'Monolith'Semiconductor''
14'August'2014'–'ARL'SiC'MOS'Workshop'
MONOLITH SEMICONDUCTOR INC. '
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Fabless'Silicon'Carbide'Power'Device'Company'
150mm'SiC'Wafer'Supplier'
''
Design'and'Process'IP'Applica@on'Knowledge'
150mm'Silicon'Foundry'
Assembly'
Customer'
• SiC'diodes'and'MOSFETs:'900VJ1.2kVJ1.7kV+'• Monolith'owns'all'SiC'design'and'SiC'process'IP'• Silicon'compa@ble'process;'fabless,'using'highJ
volume'150mm'CMOS'foundry'for'manufacturing;'lowJcost'
Incorporated'in'December'2012.'
MONOLITH SEMICONDUCTOR INC. '
Monolith’s'SiC'MOSFETs'J'Prototype'
3'
OffJstate''BV'>'1700V'
OnJstate''Rsp,on''5.5'miliohmJcm2''
• Prototypes'built'at'Cornell'University'
• Results'demonstrate'improvement'compared'to'stateJofJtheJart'
ShortJterm'stability':'Stable'aYer'225°C'stress'
Monolith Semiconductor Inc.
Supported'by'the'Cornell'NanofabricaOon'Facility'and'NaOonal'Science'FoundaOon'(Grant'ECCSS0335765)'
MONOLITH SEMICONDUCTOR INC. '
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Na@onal'Network'for'Manufacturing'Innova@on'
MONOLITH SEMICONDUCTOR INC. '
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Na@onal'Network'for'Manufacturing'Innova@on'
NNMI'objecOves:''• Focus'areas'where'the'US'is'leading'in'technology'• Strong'export'opportunity'–'growth'markets'• Provide'leadership'in'the'US'to'breakthrough'manufacturability'
and'cost'• Improve'energy'efficiency,'reduce'system'cost'
' '(e.g.'variable'speed'motor'drives)''''Monolith'Semiconductor'is'an'anchor'partner'of'the'NNMI,'focusing'on'Silicon'Carbide'device'manufacturing.'''
MONOLITH SEMICONDUCTOR INC. '
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DOE'SBIR'–'Impact'of'Cosmic'Rays'on'SiC'devices'
Project'goal:'Is'deJra@ng'necessary'for'SiC'devices?'''
lightly'doped,n'type,SiC,epitaxial,layer,
n+,SiC,substrate,
,,,,,,,,n+, ,,,,,n+,p'well, p'well,
p+, p+,
Source,Electrode,
Gate,Electrode,
Drain,Electrode,
MONOLITH SEMICONDUCTOR INC. '
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NSF'STTR'Collabora@on'with'Auburn'University'
Basic'''
lightlySdoped'nStype'SiC'epitaxial'layer'
n+'SiC'substrate'
''''''''n+' '''''n+'pSwell' pSwell'
p+' p+'
Source'Electrode'
Gate'Electrode'
Drain'Electrode'
Silicon'Carbon'
Phosphorus'
Oxygen'
Silicon'carbide'(SiC)'
Silicon'dioxide'(SiO2)'
AsSoxidized'SiC'surface'
SiC'
SiO2'
Phosphorus'passivates'dangling'
bonds'
SchemaOc'of'PotenOal'Mechanisms'of'How'Phosphorus'Improves'the'SiC/SiO2'Interface''
Project'objecOves:''Understand'the'role'of'Phosphorus'on'the'channel'mobility'and'threshold'voltage'stability'of'SiC'power'MOSFETs.''Evaluate'the'Auburn'University'“Thin'PSG”'process'on'SiC'DMOSFETs'
NaOonal'Science'FoundaOon'and'Sarit'Dhar'S'Auburn'University,'STTR'(IIPS1332039)'
MONOLITH SEMICONDUCTOR INC. '
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Key'outcomes:''The'Auburn'“thinSPSG”'achieves'superior'onSresistance'results,'even'when'applied'to'heavilySdoped'channels'of'SiC'DMOSFETs.''“ThinSPSG”'delivers'mobility'of'35'cm2/VSs'on'heavilySdoped'DMOS'pSwell''(compare'to'15'cm2/VSs'with'NO)'''Bias'Temperature'Stress'@'225°C:'IntroducOon'phosphorus'into'the'oxide'introduces'unacceptable'threshold'voltage'instability.''Also:'Phosphorus'incorporaOon'S>'poor'gate'yield''
0'
2'
4'
6'
8'
10'
12'
14'
16'
18'
0' 50' 100' 150' 200' 250'
Specific'on
Jresistance,'Vgs=15V
'''(m
Ohm
Jcm2)'
Temperature'(C)'
NO'baseline'
Thin'PSG'
S8'
S6'
S4'
S2'
0'
2'
4'
6'
5'min' 60'min'
Threshold'voltage'shiY'aYer'225
°C'
stress'at'+15'or'J1
5V'VGS'(ΔVT,'Volts)'
Stress'@me'
NO'
Thin'PSG'
Phosphorus'incorpora@on'techniques'need'significant'improvement'for'BTS,'yield.'
NSF'STTR'Collabora@on'with'Auburn'University'
MONOLITH SEMICONDUCTOR INC. '
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ARPAJe'SWITCHES'Overview'
Develop'technology'to'manufacture'wide'bandgap'switches'at'costSparity'with'silicon'IGBT'prices'<'10¢/A'''
Monolith'Semi'approach:'• Improve'the'performance'(shrink'die)'through'design'and'process'innovaOon'• UOlize'fabless'business'model'to'reduce'producOon'cost'(depreciaOon'costs)'• Manufacture'on'150mm'SiC'wafers''
ARPASe'SWITCHES'program,'SBIR'(DESAR0000442)'
MONOLITH SEMICONDUCTOR INC. '
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SiC'Process'Transfer'Requirements'
1.''Define'process'flow.''2.''IdenOfy'toolset'required'for'SiC'process'flow.''3.''Modify'tools'to'handle'transparent'SiC'wafers.'
'S'Do'not'disrupt'Silicon'processing.''S'Lead'Ome'
4.''Verify'unit'step'process'operaOon'on'SiC'wafers.''S'IdenOfy,'develop'and'demonstrate'process'changes'
required'to'achieve'required'process'capability'on'SiC'wafers''5. Evaluate'process'capability'for'each'unit'step'on'SiC'substrates'
and'epiwafers'Varia@ons'in'wafer'backside'finish'impact'tool'handling'and'processing/uniformity.'
MONOLITH SEMICONDUCTOR INC. '
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First'SiC'pin'diode'results'on'150mm'SiC'wafers'
PiN'diode'blocking'Voltage:'1700'V'Developed'basic'process'steps'for'photo,'oxides,'etc.''''Required'numerous'tool'modificaOons'and'changes'to'run'SiC'wafers.''SiC'processing'of'150mm'wafers'on'the'silicon'fabricaOon'line.'''Results:'Demonstrated'1700V'SiC'pin'diodes'on'150mm'wafers'processed'on'a'silicon'line.''''
ARPASe'SWITCHES'program,'SBIR'(DESAR0000442)'
1.2mm'x'1.2mm'
MONOLITH SEMICONDUCTOR INC. '
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Power'Electronics'Trends'
Frequency':'''''60Hz'Efficiency':'''''45%''
5W'charger'–'Past'and'Present'
60'KHz'85%''
10KW'inverter'–'Present'and'Future'
Monolith'Inside'
Frequency''':'10'KHz'Efficiency'':''92%''
100'KHz'99%''
• Compact,'higher'efficiency'power'electronics'at'same'or'lower'cost'• Volume,'weight'and'cost'dominated'by'passives'and'heat'sink'J'need'higher'
switching'frequency'and'higher'efficiency'• SiC'switches'will'enable'this'at'power'levels:'100W'to'Megawaos''
MONOLITH SEMICONDUCTOR INC. '
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Google/IEEE'Li\le'Box'Challenge'–'50'W/in3'solar'inverter!'
MONOLITH SEMICONDUCTOR INC. '
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Monolith'Semiconductor'Challenges'
What'are'the'different'values'of'verOcal'integraOon'versus'the'fabless'approach?''Control''Quality''ContaminaOon'risks''IP''Cost''
'What'is'the'real'cost'of'modifying'a'silicon'fab'to'process'SiC'wafers?''Can'we'bridge'the'technology'“valley'of'death”'inside'a'volume'producOon'facility?''Is'verOcal'vs.'fabless'the'only'approach,'or'is'there'a'suitable'middle'ground'to'ease'the'transiOon?'''Is'there'some'other'reason'that'pure'fabless'SiC'hasn’t'been'done'yet?'
'' ' 'Only'by'trying'will'we'find'out.'
'''
MONOLITH SEMICONDUCTOR INC. '
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Summary'
Monolith'Semi'is'a'fabless'SiC'device'supplier'focused'on'900S1.2kVS1.7kV+'SiC'diodes'and'MOSFETs.''We'have'demonstrated'1200V,'5.5'mOhmScm2'SiC'MOSFETs'with'stable'operaOon'at'225°C.''We'are'transferring'our'SiC'processes'into'a'highSvolume,'150'mm'silicon'foundry.''We'are'targeOng'to'run'SiC'wafers'in'parallel'with'silicon'wafers'on'the'same'process'tools.''''We'have'demonstrated'iniOal'SiC'processes,'including'demonstraOng'1700V'SiC'implanted'PiN'diodes.'''''
MONOLITH SEMICONDUCTOR INC. '
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Acknowledgments'
''Cornell'NanofabricaOon'Facility'and'the'NaOonal'Science'FoundaOon'(Grant'ECCSS0335765)''NaOonal'Science'FoundaOon'and'Sarit'Dhar'S'Auburn'University,'STTR'(IIPS1332039)'''Department'of'Energy,'SBIR'Impact'of'Cosmic'Rays'on'SiC'(DESSC0011395)''''ARPASe'SWITCHES'program,'SBIR'(DESAR0000442)''
We'appreciate'the'support'of'the'following'agencies'and'programs:''