Integration and Characterization of Low Carbon Content SiO_xC_yH_zLow κ Materials for < 0.18μm[ Dual Damascene Application

Abstract

A CVD-based low κ film was evaluated for inter-metal dielectric in < 0.18 µm generation devices. The film was deposited by conventional rf PECVD method using organosilane compound and oxygen. The measured dielectric constant of the film was 2.7~2.75. The κ value of the film was stable over several weeks and the moisture absorption was minimal. The chemical composition was in the form of SiO x C y H z , where the carbon content was less than 5 atomic %. Blanket film integration study was conducted to find out the manufacturing compatibility. The largest increase in κ value occurred during etching and ashing steps. However, SIMS compositional analysis revealed that the damage from these steps were limited to within top 300 Å, and the initial low κ value was recovered after the top damaged layer was removed by CMP. The final integrated dielectric constant was less than 3.0. The film density was measured as 1.4, compared to 2.3 g/cm 3 of conventional SiO 2 . The low density of the film resulted from the termination of SiO 2 network structures by Si-CH 3 and Si-H. INTRODUCTIONSilicon dioxide (SiO 2 ) has been dominantly applied as inter metal (IMD) and inter layer dielectric (ILD) throughout the history of microelectronics industry. The dominance is mainly attributed to its desirable electrical, thermomechanical characteristics as well as simplicity in integration with other materials. As the interconnection complexity required for high performance devices rapidly increases, however, several issues have arisen with traditional interconnection scheme, including enhanced RC delay effect, signal integrity due to cross talking and high power dissipation [1]. As part of the efforts to resolve these issues, new low dielectric constant material needs to be developed. Several approaches have been widely pursued in the past several years. Organic [2,3], inorganic [4,5] or hybrid[6,7,8] materials have been widely evaluated by either spin-on or chemical vapor deposition methods. Some of the issues with organic materials include thermal stability and reduced mechanical strength, which impose significant challenges on film integration. Inorganic low κ materials, in general, exhibit less integration issues, but κ stability still needs to be improved and there is difficulty in obtaining manufacturable materials with κ less than 3.0. Inorganic/organic hybrid material has received wide attention to obtain reliable low κ films while minimizing integration difficulties. In the development of hybrid low κ material, it is desirable to maintain low carbon content. High carbon content material has potential issues of via poisoning, etch and ash difficulties and thermomechanical instability. In this paper is presented the low carbon content low κ materials with carbon content less than 5%.

Irradiation and Humidity Effects on the Leakage Current in SiO[sub x](CH[sub 3])[sub y]-Based Intermetal Dielectric Films

“…Contrary to previously published opinion, 5 we have found evidence that humidity plays a very significant role in the electrical conductivity of both irradiated and unirradiated CORAL. Samples stored under vacuum clearly show increased leakage current density with time as the material uptakes moisture.…”

“…On the chemical stability side it is suggested that the dielectric constant of such films is stable and moisture absorption is minimal. 5 The generation ͑in terms of device size͒ of microelectronics usually found in military systems, in particular those used in a space environment, is frequently older than the current commercial one, and this is primarily because of the need to develop radiationhardened versions of them. One can therefore conclude that though low-k materials are not used presently in space applications, since they are just being integrated into commercial circuits, they will become of interest for space in the medium term.…”

Permittivity and Conductivity of Low-Dielectric-Constant SiOC:H Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

“…Different groups have investigated the physicochemical properties of SiOC:H films deposited by radio-frequency ͑rf͒ PECVD. [3][4][5][6][7][8][9][10][11][12] Usually the gas precursor is a mixture of an organosilane ͑e.g., trior tetramethylsilane͒ and an oxidizing agent ͑e.g., oxygen or nitrous oxide͒. The atomic composition appears to be strongly dependent on deposition conditions.…”

“…The atomic composition appears to be strongly dependent on deposition conditions. A compilation of past works [3][4][5][6][7][8][9][10][11][12] leads to an average film composition of 25% silicon ͑min 9%, max 42%͒, 35% oxygen ͑min 13%, max 61%͒, 20% carbon ͑min 5%, max 26%͒, and 20% hydrogen ͑min 8%, max 46%͒. IR analysis performed by numerous authors indicates the presence of Si-O-Si bonds ͑dominant͒, Si-CH 3 and Si-C-Si bonds ͑usually strong͒, Si-H and C-H bonds ͑whose intensity depends on hydrogen content, but usually small͒.…”

“…Depending on deposition methods, the dielectric constant varies between ϭ 2.5 and 4, while the optical refractive index varies between n ϭ 1.4 and 1.6. [3][4][5][6][7][8][9][10][11][12] By introducing porosity it is possible to further lower the dielectric constant ͑down to 2͒ 13 as well as the refractive index ͑1.15͒. 14 However, although not explicitly reported, 13,14 it is likely that porosity leads to a degradation of other properties ͑chemical resistance and mechanical properties͒.…”