Effects of postdeposition in situ heat treatment on the properties of low dielectric constant plasma polymer films depos
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We investigated effects of postdeposition heat treatment (HT) on the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decahydronaphthalene and tetraethyl orthosilicate as the precursors, which were referred to as plasma-polymerized decahydronaphthalene:tetraethyl orthosilicate (PPDHN:TEOS) films. HTs at 350, 450, and 500 °C decreased the relative dielectric constant k of the PPDHN:TEOS films from 3.16, the k value of the as-deposited film, to 2.82, 2.72, and 3.02, respectively. The change of k value as a function of HT temperature was correlated with the change of Fourier transform infrared absorption peaks of O–H, C⳱O, and Si-related groups. As the HT temperature increased, the thermal stability of the PPDHN:TEOS film increased. PPDHN:TEOS films, as-deposited or heat treated, showed leakage current density in the order of 10−7 A/cm2 at 1 MV/cm.
I. INTRODUCTION
As device features in next-generation integrated circuits continue to shrink, resistance × capacitance delay greatly limits chip performance and reliability due to the increased power dissipation and metal line cross-talk in multilevel interconnects.1 It is necessary to replace the present interlayer dielectric SiO2 with the relative dielectric constant k ∼ 4.1 by materials with a low dielectric constant (low-k: k 艋 3.5). Plasma enhanced chemical vapor deposition (PECVD) of low-k films has been studied intensively due to advantages of the PECVD method as a semiconductor manufacturing method. PECVD can produce thin films with excellent large area uniformity and can be easily integrated into the vacuum processes of the present semiconductor manufacturing. PECVD using hydrocarbon precursors can produce so-called “plasma polymers.” Plasma polymers are quite different from chemically synthesized polymers.2 The former have highly cross-linked structures of random bonding environments while the latter have chains of regular repeating units. Many research groups reported the deposition and characterization of plasma polymer films as low-k materials.3–7 In plasma polymer films deposited using
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 6, Jun 2002
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hydrocarbon precursors, such as toluene, benzene, and para-xylene, obtaining both low-k values and high thermal stability is quite challenging. In previous works, it was revealed that decreasing k values of plasma polymers accompanied decreasing thermal stability.5–7 Considering that plasma polymer films deposited using hydrocarbon precursors show relatively low k values and films containing Si atoms in their atomic networks are more thermally stable than plasma polymer films deposited with only pure hydrocarbons, PECVD deposition using a mixture of a hydrocarbon precursor and a Si-containing precursor is expected to produce films with both low k values and high thermal stability. Several groups deposited low-k films using a mixture of hydrocar
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