Polymerization for Highly Selective SiO<sub>2</sub> Plasma Etching

Samukawa, Seiji; Furuoya, Shuichi

doi:10.1143/jjap.32.l1289

Cited by 21 publications

(7 citation statements)

References 3 publications

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“…In particular, numerous groups have reported strong correlation between the gasphase CF 2 radical concentration and the polymer deposition rate ͑and thus to the etch selectivity͒. [17][18][19][20][21][22][23] It was therefore suggested 17,24 that the film is formed simply by the sticking of CF 2 radicals on the silicon surface, forming a poly tetra fluoroethylene ͑PTFE͒-like (CF 2 ) n film. However, several other neutral molecules ͑e.g., CF, 25 CF 3 , 11 C 2 F 5 , 11 C 4 F 2 25 ͒ have also been proposed as the polymer precursors.…”

Section: B the Role Of Cf X Radicalsmentioning

confidence: 99%

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

Cunge

Booth

1999

Journal of Applied Physics

174

117

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Articles you may be interested inStudy of Ti etching and selectivity mechanism in fluorocarbon plasmas for dielectric etchThe study of CF and CF 2 radical production and loss mechanisms in capacitively-coupled 13.56 MHz CF 4 plasmas has been extended to CF 4 plasmas with an Si substrate, and to C 2 F 6 plasmas, conditions where the atomic fluorine concentration is lower and where more polymer deposition occurs on the reactor surfaces. Processes in the gas phase and at the reactor surfaces were investigated by time resolved axial concentration profiles obtained by laser induced fluorescence, combined with absolute calibration techniques. The results for CF were similar to those observed in the fluorine rich case, whereas the results for CF 2 were strikingly different and more complex. This paper focuses on the CF 2 radical, which, under these conditions is produced at all of the surfaces of the reactor, apparently via a long-lived surface precursor. The results can only be explained if large polymeric ions and/or neutrals are produced by polymerization in the gas phase. The gas-phase CF 2 concentration is high, causing the otherwise slow gas-phase concatenation reactions C X F Y (CF 2 ) n ϩCF 2 →C X F Y (CF 2 ) nϩ1 to occur. These processes produce high-mass neutrals ͑and ions͒ which are the real polymer precursors. The CF 2 radical therefore circulates in a closed cycle between the surface and the gas phase. The degree of polymerization is controlled by the fluorine atom concentration, which simultaneously controls the concentrations of CF 2 , of chain initiating species such as CF 3 and of dangling bonds on the growing oligomers. This model appears to apply to fluorocarbon discharges in general, and agrees well with other results presented in the literature.

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Section: B the Role Of Cf X Radicalsmentioning

confidence: 99%

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

Cunge

Booth

1999

Journal of Applied Physics

174

117

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“…The area contributions of C-C, C*-CF, CF, CF 2 and CF 3 to the overall spectrum area are 7, 25, 22,26 and 20%, respectively (72 ). The slightly greater amount of CF 2 is typical of plasma fluoropolymers and reflects the more active role of CF 2 in the polymerization reaction (15)(16)(17)(18) The slightly smaller amounts of CF and CF 3 and the formation of C-C and C*-CF groups can be associated with monomer fragmentation and etching. The release of atomic fluorine (7,75 ) and the participation of the CF 3 + ion in etching have been observed (2 ).…”

Section: Resultsmentioning

confidence: 99%

Film Formation in Hexafluoropropylene Plasmas

Silverstein

Chen

1996

ACS Symposium Series

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The gas phase dominated plasma polymerization (PP) of hexafluoropropylene (HFP) produces 0.2 to 0.5 μm particles and 1 μm spherical particle agglomerates which are all incorporated into a transparent and highly adhering PPHFP film. An energy ratio plasma parameter, E, related to the plasma energy and strongly dependent on flow rate (or residence time) was derived. The maximum and plateau in deposition were successfully described when polymerization and etching were exponentially related to E. The chemical structure of the amorphous, crosslinked PPHFP consists largely of similar amounts of C*-CF, CF, CF 2 and CF 3 units. Plasma etching was inhibited by fluorine scavenging and HF formation on the addition of hydrogen to the feed. The deposition and coalescence of smaller particles into a smoother and more uniform surface on adding nitrogen reflects the incorporation of nitrogen into the polymer, the increase in the polar component of surface energy and, perhaps, the decrease in dominance of gas phase versus surface polymerization. The low PP(N 2 /HFP) electrical breakdown strength may be attributed to an alternate conduction mechanism in the relatively polar plasma fluoropolymer.Thin fluoropolymer films can have many advantages including a low coefficient of friction, a low surface energy, thermal stability, biocompatibility, and chemical resistance. Unfortunately, the techniques used to deposit thin films of conventional fluoropolymers can involve etchants, solvents and temperatures that limit their applicability. Plasma polymerization is an ambient temperature, solvent-free process that can be used to deposit highly adhering, pinhole-free and crosslinked thin fluoropolymer films from a variety of compounds including those not polymerizable by standard techniques (7-3). These films would have potential applications in the microelectronics, biomedical, membrane, aerospace and automotive fields (4-9).

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“…1,2 The complexity of fluorocarbon plasmas comes from the fact that many types of radicals and ions coexist and contribute differently to surface processes, resulting in simultaneous deposition of polymer passivation layers at surfaces ͑walls and wafer͒ during wafer etching. 14,15 The etch rate of Si or SiO 2 is sensitive to the thickness of the polymeric layer which is formed by C x F y deposition, usually decreasing with increasing polymer thickness. On the other hand, polymer passivation of the sidewall helps in obtaining anisotropic etch profiles.…”

Section: Cf 4 Plasma and Surface Reaction Mechanisms For Cf 2 Prmentioning

confidence: 99%

Mechanisms for CF2 radical generation and loss on surfaces in fluorocarbon plasmas

Zhang

Kushner

2000

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Polymerization for Highly Selective SiO₂ Plasma Etching

Cited by 21 publications

References 3 publications

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

Film Formation in Hexafluoropropylene Plasmas

Mechanisms for CF2 radical generation and loss on surfaces in fluorocarbon plasmas

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Polymerization for Highly Selective SiO2 Plasma Etching

Cited by 21 publications

References 3 publications

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

CF 2 production and loss mechanisms in fluorocarbon discharges: Fluorine-poor conditions and polymerization

Film Formation in Hexafluoropropylene Plasmas

Mechanisms for CF2 radical generation and loss on surfaces in fluorocarbon plasmas

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Product

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Polymerization for Highly Selective SiO₂ Plasma Etching