Low dielectric constant fluorocarbon films containing silicon by plasma enhanced chemical vapor deposition

Use of low relative dielectric constant (low-k) material as an interlayer dielectric is among important approaches to reduce the RC time delay in high performance ultra-large-scale integrated circuits. Copper metallization is another approach besides the use of low-k material, in reducing the RC delay time, because of its well-known characteristics of low resistivity and high electromigration resistance. Fluorocarbon films containing silicon (SiCF) have been developed in this work for low-k interlayer dielectric applications below 50 nm linewidth technology. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) using gas precursors of tetrafluoromethane as the source of active species and disilane (5 % by volume in helium) as both an active species source and a reducing agent to control the ratio of fluorine to carbon in the films. The basic properties for these low-k interlayer dielectric films were studied along with characterization of their fabrication process. Electrical, mechanical, chemical and thermal properties were evaluated including dielectric constant, electrical field strength, surface planarity, residual stress, hardness, chemical bond structure, and shrinkage upon heat treatment. Deposition process conditions were optimized for film thermal stability while maintaining a relative dielectric constant value as low as 2.0. The average breakdown field strength of the SiCF films was 4.74 MV/cm and its optical energy gap was in the range of 2.2 to 2.4 eV. The hardness and residual stress in the SiCF films deposited under the optimized conditions were respectively measured to be in the range of 1.4 to 1.78 GPa and in the range of 11.6 to 23.2 MPa of compressive stress. For integrated microsystems as well as for ULSI circuits, surface modification of SiCF films by wet chemical treatment and by X-ray irradiation were examined to facilitate copper metallization. Feasibility of copper deposition by recently developed electroless techniques is discussed in conjunction with the studies utilizing wet chemical modification of the film surface. The effect of X-ray irradiation on the chemical structure of the films is also discussed. Additionally, means for selective surface modification of the films are introduced by exposing the films through an X-ray mask

Investigation Of Reactively Sputtered Boron Carbon Nitride Thin Films

Research efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For this purpose, B-C-N ternary system which is based on carbon, boron and nitrogen which exhibit exceptional properties and attract much attention from mechanical, optical and electronic perspectives. Also, boron carbonitride (BCN) thin films contains interesting phases such as diamond, cubic BN (c-BN), hexagonal boron nitride (h-BN), B4C, β-C3N4. Attempts have been made to form a material with semiconducting properties between the semi metallic graphite and the insulating h-BN, or to combine the cubic phases of diamond and c-BN (BC2N heterodiamond) in order to merge the higher hardness of the diamond with the advantages of c-BN, in particular with its better chemical resistance to iron and oxygen at elevated temperatures. New microprocessor CMOS technologies require interlayer dielectric materials with lower dielectric constant than those used in current technologies to meet RC delay goals and to minimize cross-talk. Silicon oxide or fluorinated silicon oxide (SiOF) materials having dielectric constant in the range of 3.6 to 4 have been used for many technology nodes. In order to meet the aggressive RC delay goals, new technologies require dielectric materials with

Synthesis and characterization of low pressure chemically vapor deposited boron nitride and titanium nitride films

This study has investigated the interrelationships governing the growth kinetics, resulting compositions, and properties of boron nitride (B-C-N-H) and titanium nitride (Ti-N-Cl) films synthesized by low pressure chemical vapor deposition (LPCVD) using ammonia (NH3)/triethylamine-borane and NH3/titanium tetrachloride as reactants, respectively.Several analytical methods such as the FTIR, UVNisible spectroscopy, XPS, AES, RBS, SEM, and XRD were used to study the stoichiometry and structure of the deposited films. The B-N-C-H films were synthesized over a temperature range of 300 to 8500C at various flow rate ratios of the reactants and total pressure range of 50 to 150 mTorr. The deposits were amorphous in all cases having an index of refraction ranging between 1.76 and 2.47 depending on the composition of the films. The stress of the deposited films varied from +240 to -200 Wa, depending on the deposition parameters. The hardness and Young\u27s modulus were found to be between 5 to 12 GPa and 50 to 120 GPa, respectively. Electrical properties of the BN films were measured using metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures. The films did not react with water vapor and exhibited dielectric constant between 3.12 and 5.5. Free standing X-ray windows with thickness varying from 2000Å to 12,000Å, were fabricated using the mildly tensile and compressive films and X-ray transmission studies through these windows indicate significantly lower absorption when compared to the commercially available polymeric X-ray windows. The Ti-N-Cl deposits exhibited an Arrhenius d ependence in the deposition temperature regime of 450 to 600 °C from which an activation energy of ~42 kJ/mol was calculated. The growth rate dependencies on the partial pressures of NH3 (50 to 100 mTorr) and TiC14 (1 to 12 mTorr) yielded reaction rate orders of 1.37 and -0.42 respectively. Films with compositions trending towards stoichiometry were produced as the deposition temperature was decreased and the NH3 partial pressure was increased. The chlorine concentration in the films was observed to decrease from ~8 % (a/o) at the deposition temperature of 450 °C down to ~0.2 % (a/o) at 850 °C. The film density values increased from 3.53 to 5.02 g/cm3 as the deposition temperature was increased from 550 to 850 °C. The resistivity of the films was dependent on changes in deposition temperature and flow rate ratios. The lowest resistivity value of 86 µΩcm was measured for a deposition temperature of 600°C and an NH3/TiCl4 flow ratio of 10/1. The film stress was found to be tensile for all deposits and to decrease with higher deposition temperatures. Nanoindentation measurements yielded values for the hardness and Young\u27s modulus of the films to be around 15 and 250 GPa, respectively. X-ray diffraction measurements revealed in all cases the presence of cubic TiN phase with a preferred (200) orientation. For the investigated aspect ratios of up to 4: 1, the deposits were observed to exhibit conformal step coverage over the investigated range of processing conditions

Porous Low-Dielectric-Constant Material for Semiconductor Microelectronics

To provide high speed, low dynamic power dissipation, and low cross-talk noise for microelectronic circuits, low-dielectric-constant (low-k) materials are required as the inter- and intra-level dielectric (ILD) insulator of the back-end-of-line interconnects. Porous low-k materials have low-polarizability chemical compositions and the introducing porosity in the film. Integration of porous low-k materials into microelectronic circuits, however, poses a number of challenges because the composition and porosity affected the resistance to damage during integration processing and reduced the mechanical strength, thereby degrading the properties and reliability. These issues arising from porous low-k materials are the subject of the present chapter

Investigation of paraelectric PTL thin films using reactive magnetron sputtering

The study of methods to prepare paraelectric perovskite PLT (Pb1-xLaxTi1-x/4O3; x=0.28) thin films has been important because thin films of this high dielectric strength material are required to make high density capacitors for dynamic random access memory. In this research, paraelectric PLT thin films were prepared on multi-layer (Pt/Ti/SiO2/Si) and MgO substrates in a unique way by the reactive magnetron sputtering method using a multi-component metal target. The individual control of each metal area on the sputtering target had considerable influence on the stoichiometry and electrical properties of the thin films. The effect of post-deposition annealing on as-deposited amorphous PLT films was studied as a function of temperature in the range of 450 °C to 750 °C. The interdependent relationship of the composition, crystalline structure and surface morphology in the films was studied as a function of annealing conditions. The chemical composition of the as-deposited and annealed films was measured by Rutherford back-scattering (RBS) and Auger electron spectroscopy (AES). The composition of PLT (28) thin film was: Pb, 0.73; La, 0.28; Ti, 0.88; 0, 2.9. The dielectric constant ([epsilon]r) and dissipation factor (tan [delta]) at low electric field measurement (500 V/cm) of the capacitors with the highest dielectric properties were 1216 and 0.018, respectively. Single crystal film at 650 °C were smooth and had the lowest leakage current density, 0.1 μA/cm2, at the electric field of 0.25 MV/cm. However, the highest dielectric constant, 1216, and the highest charge storage density, 12.5 μC/cm2, obtained with an annealing temperature of 750 °C. The research showed that magnetron sputtering can be used to prepare paraelectric perovskite PLT (28) thin films with high dielectric constant, large charge storage density and relatively low leakage current for capacitor applications in active DRAM cells

Chemical vapor deposition and characterization of polysilanes polymer based thin films and their applications in compound semiconductors and silicon devices

As the semiconductors industry is moving toward nanodevices, there is growing need to develop new materials and thin films deposition processes which could enable strict control of the atomic composition and structure of thin film materials in order to achieve precise control on their electrical and optical properties. The accurate control of thin film characteristics will become increasingly important as the miniaturization of semiconductor devices continue. There is no doubt that chemical synthesis of new materials and their self assembly will play a major role in the design and fabrication of next generation semiconductor devices. The objective of this work is to investigate the chemical vapor deposition (CVD) process of thin film using a polymeric precursor as a source material. This process offers many advantages including low deposition cost, hazard free working environment, and most importantly the ability to customize the polymer source material through polymer synthesis and polymer functionalization. The combination between polymer synthesis and CVD process will enable the design of new generation of complex thin film materials with a wide range of improved chemical, mechanical, electrical and optical properties which cannot be easily achieved through conventional CVD processes based on gases and small molecule precursors. In this thesis we mainly focused on polysilanes polymers and more specifically poly(dimethylsilanes). The interest in these polymers is motivated by their distinctive electronic and photonic properties which are attributed to the delocalization of the [sigma]-electron along the Si-Si backbone chain. These characteristics make polysilane polymers very promising in a broad range of applications as a dielectric, a semiconductor and a conductor. The polymer-based CVD process could be eventually extended to other polymer source materials such as polygermanes, as well as and a variety of other inorganic and hybrid organic-inorganic polymers. This work has demonstrated that a polysilane polymeric source can be used to deposit a wide range of thin film materials exhibiting similar properties with conventional ceramic materials such as silicon carbide (SiC), silicon oxynitride (SiON), silicon oxycarbide (SiOC) silicon dioxide (SiO[subscript 2]) and silicon nitride (Si[subscipt 3]N[subscript 4]). The strict control of the deposition process allows precise control of the electrical, optical and chemical properties of polymer-based thin films within a broad range. This work has also demonstrated for the first time that poly(dimethylsilmaes) polymers deposited by CVD can be used to effectively passivate both silicon and gallium arsenide MOS devices. This finding makes polymer-based thin films obtained by CVD very promising for the development of high-[kappa] dielectric materials for next generation high-mobility CMOS technology

Characterization of low k CVD deposited interlayer dielectrics for integrated circuits

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997.Includes bibliographical references (leaves 62-66).by Marnie L. Harker.M.S

Plasma Damage on Low-k Dielectric Materials

Low dielectric constant (low-k) materials as an interconnecting insulator in integrated circuits are essential for resistance-capacitance (RC) time delay reduction. Plasma technology is widely used for the fabrication of the interconnects, such as dielectric etching, resisting ashing or stripping, barrier metal deposition, and surface treatment. During these processes, low-k dielectric materials may be exposed to the plasma environments. The generated reactive species from the plasma react with the low-k dielectric materials. The reaction involves physical and chemical effects, causing degradations for low-k dielectric materials. This is called “plasma damage” on low-k dielectric materials. Therefore, this chapter is an attempt to provide an overview of plasma damage on the low-k dielectric materials

Chemical vapor deposition of thin films for ULSI interconnect metallization

We have studied the kinetics of copper chemical vapor deposition (CVD) for interconnect metallization using solution delivery of Cu(hfac)2 (Cu(II) hexafluoroacetyl-acetonate) dissolved in isopropanol. We observe a growth rate of 17.7 „b 1.5 nm/min at reference conditions of 300„aC substrate temperature, 0.025 Torr Cu(hfac)2 partial pressure, 1.6 Torr isopropanol (reducing agent), and 80 Torr H2 (carrier gas). The film resistivity approaches the bulk value of copper for film thickness greater than 100 nm. Reaction order experiments show first-order kinetics with respect to Cu(hfac)2 partial pressure and zero-order with respect to isopropanol. A series reaction mechanism including three kinetically significant steps (adsorption of Cu(hfac)2, dissociation of (hfac) ligand, and desorption of (hfac)) is used to describe the observed kinetic results. The proposed rate determining step is the dissociation of (hfac) ligand when the pressure ratio of Cu(hfac)2 to isopropanol is low, and becomes the desorption of (hfac) when the pressure ratio is high. We also examined a low temperature chemical vapor deposition process for the growth of tantalum thin films using SiH4 reduction of TaF5. Using a temperature of 350„aC and reactant partial pressures of 0.2 Torr TaF5 and 0.3 Torr SiH4, we obtain a growth rate of 2.2 ¡Ó 1.7 nm/min. The XPS analysis results show that the Ta film is Si free, but contains relatively high oxygen concentration because of residual gas contamination. Lastly, we have studied a batch CVD process for palladium seed layer deposition using H2 reduction of Pd(hfac)2 (Pd(II) hexafluoroacetylacetonate). Nano-sized Pd particles with nuclei density between 1 to 14 clusters/ƒÝm2 are observed using AFM. The quality of the Pd seed layer is examined by depositing electroless copper film. We have investigated the influence of CVD operating conditions (deposition time, activation temperature, and precursor concentration) on the activity of the Pd seed layers (i.e., by monitoring visual appearance and deposition rates of the ELD Cu films). At the optimized conditions we can deposit uniform Cu films at a rate of 3.4 „b 1.4 nm/s. Additional work is needed to improve the resistivity and adhesion of the films