1 Impact of SiOC Low K Materials on Dual Damascene Patterning Impact of SiOC Low K Materials on Dual Damascene Patterning Gary Ray, Ph.D Steve Lassig Director, Integration Sr. Manager, Integration Novellus Systems, Inc. Lam Research, Inc. Gary Ray, Ph.D Steve Lassig Director, Integration Sr. Manager, Integration Novellus Systems, Inc. Lam Research, Inc.
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Impact of SiOC Low K Materials on Dual Damascene Patterning...Impact of SiOC Low K Materials on Dual Damascene Patterning Gary Ray, Ph.D Steve Lassig Director, Integration Sr. Manager,
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Impact of SiOC Low K Materials on DualDamascene Patterning
Impact of SiOC Low K Materials on DualDamascene Patterning
Gary Ray, Ph.D Steve LassigDirector, Integration Sr. Manager, IntegrationNovellus Systems, Inc. Lam Research, Inc.
Gary Ray, Ph.D Steve LassigDirector, Integration Sr. Manager, IntegrationNovellus Systems, Inc. Lam Research, Inc.
2Novellus and Lam Research Confidential 2-14-02
AcknowledgementAcknowledgement
The members of the integration organizations ofLam Research, Inc. and Novellus Systems, Inc.
The members of the integration organizations ofLam Research, Inc. and Novellus Systems, Inc.
3Novellus and Lam Research Confidential 2-14-02
Presentation OutlinePresentation Outline
➤ Dual damascene process flow.➤ Dual damascene etch challenges.➤ Photoresist poisoning.➤ Trench etch.➤ Via etch.➤ Trench-over-via etch.➤ Barrier open etch.➤ Summary
➤ Dual damascene process flow.➤ Dual damascene etch challenges.➤ Photoresist poisoning.➤ Trench etch.➤ Via etch.➤ Trench-over-via etch.➤ Barrier open etch.➤ Summary
General Dual Damascene Etch Challenges CVD SiOC Low k Film Issues➤ Carbon content➤ Chemical reactivity➤ Reduced density
Cu
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DUV Resist PoisoningDUV Resist Poisoning
➤ Amines poison DUV photoresist, preventing development.➤ Amines enter dielectric stacks from a number of sources.➤ The phenomenon has been reported for most classes of low k films.➤ Amines diffuse rapidly in low density low k films.
➤ Amines poison DUV photoresist, preventing development.➤ Amines enter dielectric stacks from a number of sources.➤ The phenomenon has been reported for most classes of low k films.➤ Amines diffuse rapidly in low density low k films.
poisoned resist
X-section view
via structureafter trenchlithography
After trench etch.
7Novellus and Lam Research Confidential 2-14-02
DUV Resist PoisoningDUV Resist Poisoning
➤ Nitrogen in dielectric deposition processes (N2O, NH3) is theprimary cause of DUV resist poisoning.
➤ Nitrogen can enter SiOC layers during barrier film pre-deposition set-up steps and during the actual depositions.
➤ Etch and strip steps are of secondary importance at best.➤ The source material, as well as the reactor must not inject N2
into the process chamber.
➤ Nitrogen in dielectric deposition processes (N2O, NH3) is theprimary cause of DUV resist poisoning.
➤ Nitrogen can enter SiOC layers during barrier film pre-deposition set-up steps and during the actual depositions.
➤ Etch and strip steps are of secondary importance at best.➤ The source material, as well as the reactor must not inject N2
into the process chamber.ILD stack with NHx contamination NHx eliminated from stack
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Trench Etch - Metal 1Trench Etch - Metal 1
➤ Metal 1 trench etch is the least demanding process.• Low aspect ratios.• Etch stops used.
➤ M1 Etch Issues• CD control.• Profile control.• Microloading.• Uniformity.• Selectivity to barrier film.
➤ Followed by barrier open step to expose W plugs.
➤ Metal 1 trench etch is the least demanding process.• Low aspect ratios.• Etch stops used.
➤ M1 Etch Issues• CD control.• Profile control.• Microloading.• Uniformity.• Selectivity to barrier film.
➤ Followed by barrier open step to expose W plugs.
SiC
SiOC
SiCCu
M1 Lines in SiOC low k film.
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Trench Etch - Metal 1Electrical Data versus Process PerformanceTrench Etch - Metal 1Electrical Data versus Process Performance
SiC
SiOC
SiCCu
M1 lines in SiOC low k film.Optimized process.
SiC
SiOC
SiC
Cu
M1 lines in SiOC low k film.Bowing and cusping.
Optimized process
Optimized process
10
12
14
16
18
20
0 5 10 15 20 25 30 35 40
M1
serp
. res
ista
nce
(k)
56789
101112131415
0 5 10 15 20 25 30 35 40
M1
com
b ca
paci
tanc
e (p
F)
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Via Etch ChallengesEtch StopVia Etch ChallengesEtch Stop
➤ The carbon content of CVD SiOC films can cause “etch stop.”• Attainable etch depth is dependent on etch selectivity.• Multi-step via etches are often employed.• Independent control of plasma density and ion energy is desirable.
➤ The carbon content of CVD SiOC films can cause “etch stop.”• Attainable etch depth is dependent on etch selectivity.• Multi-step via etches are often employed.• Independent control of plasma density and ion energy is desirable.
Resist
ARL
Coral
SiC:H
0.25 Via “etch-stopped”at a depth of ~0.6µm
0
5
10
15
20
1 1.2 1.4 1.6
etch stop depth, µm
Cor
al:b
arrie
r sel
ectiv
ity
SiNSiC
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Via Etch ChallengesChemical ReactivityVia Etch ChallengesChemical Reactivity
➤ The Si-CH3 groups in CVD SiOC films are susceptible toattack by fluorine and oxygen atoms.
➤ Protective polymer thickens toward the via bottoms.➤ Overetch process must be optimized for minimal bowing.
➤ The Si-CH3 groups in CVD SiOC films are susceptible toattack by fluorine and oxygen atoms.
➤ Protective polymer thickens toward the via bottoms.➤ Overetch process must be optimized for minimal bowing.
Resist
ARL
Coral
SiC:H
0.25 Via etched to adepth of 1.0µm
Via bowing caused byoveretch step.
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Trench-over-Via Etch: The most demandingprocess.Trench-over-Via Etch: The most demandingprocess.
Many demands must be metsimultaneously.
➤ Trench profile and CDcontrol.
➤ Smooth trench bottom.➤ Protection of barriers in vias.➤ Via profile maintenance.➤ Control of “terracing” and
veil formation.
Many demands must be metsimultaneously.
➤ Trench profile and CDcontrol.
➤ Smooth trench bottom.➤ Protection of barriers in vias.➤ Via profile maintenance.➤ Control of “terracing” and
veil formation.
SiO2
SiOC
SiC
Progression of T/V etch in 0.25µm via chain feature,Resist and I-line plugs have been stripped in-situ.