We studied in detail the paramagnetic defect generated in the porous low-k SiOCH films, which is called the T b center with the oxygen-carbon mixed back bonds. We baked the SiOCH films in vacuum from 600 to 1000°C, which could correspond to temperature elevation at a local area in cases of UV or electron-beam curing and Joule heating in circuits. The amount of the T b center increased abruptly around 775°C by electron spin resonance spectroscopy, at which we observed 30% volume shrinkage by ellipsometry and network change from a cage link to a ring link by Fourier transform IR spectroscopy. These phenomena might be due to the crush of microholes wrapping Si-CH 3 end groups. Therefore, we consider that the generation of the T b center suggests the quality change of the porous low-k SiOCH films for the ultralarge-scale integration reliability.As device densities increase in ultralarge-scale integration ͑ULSI͒ semiconductor chips, the signal propagation delay in multilevel interconnects becomes more critical for device performance. SiOCH films ͑silicon oxide containing hydrocarbon groups, k = 3.0͒ have been used for the low-dielectric-constant ͑low-k͒ dielectrics of the most advanced ULSI interconnects because of their high compatibility with the silicon process. 1 Recently, the nanometer level pores in a SiOCH film have been introduced to reduce k ͑Ͻ2.7͒. 2 The porous low-k SiOCH films have a lower mechanical strength than the conventional dielectric films. So, the porous SiOCH films were cured by UV light exposure or electron-beam ͑EB͒ irradiation to enhance mechanical strength. 3,4 However, the defects, called the T b centers having oxygen-carbon mixed back bonds, can be generated in the porous SiOCH films by excess UV/EB curing. 3,5-7 The generation of paramagnetic defect ͑T b center͒ is thought to be one of the ULSI interconnect reliability issues. In this work, we investigated in detail the behavior of the T b center in the porous low-k SiOCH films using vacuum baking instead of UV/EB curing. UV curing ͑high energy photon; about 5 eV͒ corresponds to local annealing, and vacuum baking ͑low energy phonon; at most 0.1 eV͒ corresponds to uniform annealing. Both processes are thought to give rise to the same microstructure change. We used an electron spin resonance ͑ESR͒ technique to detect the defects, ellipsometry to measure the film thickness and refractive index, and Fourier transform infrared ͑FTIR͒ spectroscopy to analyze the atomic network in the porous low-k SiOCH films. ExperimentalSample preparation.-The 500 nm thick, porous low-k SiOCH films ͑k = 2.6͒ were deposited on 300 mm ͑100͒ silicon wafers ͑10-15 ⍀ cm͒ with plasma-enhanced chemical vapor deposition. The film composition was determined to be Si:O:C:H = 1.0:1.7:0.9:2.9 by Rutherford backscattering analysis. 7 To actualize the defects in the low-k films, the samples were baked up to 1000°C in the vacuum chamber ͑15-25 Pa͒, where the samples were maintained at a certain setup temperature for 30 min and taken out below 300°C.Characterization.-The ESR m...

We have studied in detail the paramagnetic defect generated in the porous low-k SiOCH films, which is called as T b center with the oxygen-carbon mixed back bonds. We baked the SiOCH films in vacuum at the temperature from 600 o C to 1000 o C, which could correspond to local temperature enhancement when UV/EB curing and Joule heating in circuits. We have found that the amount of the T b center increased abnormally around the temperature 775 o C by ESR spectroscopy. Moreover, we have observed 30%-volume shrinkage by ellipsometry and network change from cage link to ring link by FTIR spectroscopy. These phenomena might be concerned to a crush of micro holes wrapping Si-CH 3 end groups.Therefore, we consider that the generation of the T b center indicates the quality change of the porous low-k SiOCH films as for the ULSI reliability.