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The Last Puzzle toward Cost-Effective FEOL CMP Processing:
New-generation Cleaner for Positive-charged Silica Slurry
Cleaning Principle
Technical Issue
Introduction
Jhih-Fong Lin*, Paul Bernatis, Pei-Yu Tai, Chia-Hui Bai, Eric Lee, Wen-Hsuan Chang, Ling Chang, Akira Kuroda and Chi Yen
EKC Technology, DuPont
Dupont Confidential
PCMP Cleaning Evaluation
Conclusions
Oxide(silica) removal is the most time/cost-consuming application in FEOLCMP (chemical mechanical planarization) processing. Recently, positively-charged silica with lower cost of ownership indicates another direction inCMP processing. With tailored surface engineering on abrasives, this kindof slurry can greatly enhance the interaction between abrasive and desiredpolished surface, as a result enables elimination of solid content at pointof use. On the other hand, the enhanced affinity (also removal rate) ofpositive-charged silica to polished surface brings out the additionalcleaning issue in practice which commodity chemistry couldn’t help.
Strong repulsion force results in excellent performance
EKC-5710 would give strong electrostatic repulsion force between TEOS/SiNsurface and slurry particle
Clean Configuration* Mega Brush 1 Brush 2
Commodity Clean Alkaline dHF Alkaline
Formulation Clean Alkaline EKC-5710 Alkaline
(i)Tool: AMAT; (ii) Inspection: KLA-SP2 (iii) Target: TEOS/HDP; (iv) Cabot D9228 slurry
0.40 0.380.30 0.21
0%
20%
40%
60%
80%
100%
120%
Recipe 1 Recipe 2 Recipe 3 Recipe 4
Norm
alize
d D
efe
ctiv
ity
(0.1
2μm)
Cleaning performance through varying recipe
Commodity Clean Formulation Clean
0 200 400 600 800 1000 1200
Binding Energy (eV)
XPS of Treated TEOS
Blank
Commodity
EKC-5710
Cleaner TEOS SiN PolySilicon
Compatibility (Å /min)dHF (0.5%) 63 3 <1
EKC-5710 <1 <1 <1
(i) Great material compatibility to dielectric surface (ii) No organic residue/contamination
(iii) Broaden cleaning window versus commodity chemistry
EKC-5710 provides a total-solution to acidic/positive charged silica slurry PCMP processing
(a)
(b) (c)Traditional Colloidal Silica(negative-charged in acidic region)
SiO2 SiO2
TEOS wafer
Repulsion
Acidic Silica(positively-charged in acidic region
TEOS wafer
SiO2SiO2
Attraction
Positively-charged silica CMP has been widely applied for ILD and STI Processing, the reverse surface charge makes acidic silica abrasive with higher TEOS removal efficiency. Meanwhile, the electrostatic attraction force also pose another technical challenge in PCMP cleaning. With tailored surface engineering on positively-charged silica and TEOS surface, EKC-5710 enables strong repulsion force and prevents the particle redeposition during the PCMP cleaning process. In addition, EKC-5710 also demonstrates promising dielectric compatibility without the organic residue/contamination left on cleaned surface. On the other hand, EKC-5710 also shown much broaden working window than commodity chemistry. The enhancement of defect removal indicates EKC-5710 reduces significant amountof particular defect that could be last puzzle toward the low-cost ownship FEOLCMP process.
Figure 1. interaction of different silica abrasives to TEOS surface
Figure 2. (a) Material compatibility of commodity chemistry and EKC 5710; (b) Surface analysis of wet-cleaned TEOS wafer; (c) PCMP cleaning performance upon positively-charged silica CMP.
