Density Plasma Chemical Vapor Deposition Research Articles

Effect of Fluorine on Characteristics of Shallow Trench Isolation Prepared Using High-Density Plasma Chemical Vapor Deposition Including NF3 Chemistry

We investigated whether the fluorine of the field oxide affected gate oxide reliability and some isolation characteristics of metal–oxide semiconductor (MOS) transistors for high-density dynamic random-access memory (DRAM). Fluorine was incorporated during high density plasma (HDP) chemical vapor deposition (CVD) using NF3 chemistry for better shallow trench isolation (STI) gap-filling ability. Considerable fluorine included in the field oxide during deposition diffused from the field oxide to the silicon surface of a shallow trench during the subsequent thermal processes. This fluorine of the field oxide did not degrade the gate oxide reliability such as SILC and charge-to-breakdown characteristics. Moreover, it could improve various transistor characteristics such as the junction leakage, isolation punch-through current and data retention time of a DRAM device. It was inferred that some improvement of the MOS transistor was obtained by the interaction of Si interface traps near the trench wall with fluorine and the reduction of the density of Si interface traps.

Deposition temperature determination of HDPCVD silicon dioxide films

High density plasma chemical vapor deposition (HDPCVD) is a widely used technique in semiconductor integrated circuit (IC) manufacturing, especially to form inter-metal silicon (IMD) dioxide thin films. It was designed for commercially available tools in order to satisfy the gap filling requirements necessary for 0.18 and 0.15 μm technology ICs, but it has been successfully extended also for 0.13 μm technological node and over. HDPCVD technique has a potential impact on device electrical characteristics and metallurgy compatibility, according to process conditions, such as deposition temperature. The work here presented deals with some physical–chemical characteristics of the HDPCVD deposited thin un-doped silicate glass (USG) films used in IC architecture. In a particular way, the dependence of the Si–OH bond concentration, revealed by FTIR, wet etch rate ratio compared with thermal SiO 2 and hydrogen content, determined by elastic recoil detection analysis (ERDA), are correlated with deposition temperature. The results demonstrate how it is possible after film deposition to reveal from the HDPCVD USG film itself which real temperature it has been deposited at, allowing a practical method in production environment for statistical process control.

Characterization and thermal stability of fluorosilicate glass films deposited by high density plasma chemical vapor deposition with different bias power

High-density plasma chemical vapor deposition (HDP-CVD) fluorosilicate glass (FSG) films were evaluated for the application of inter-metal dielectric (IMD) materials in current devices. Film characteristics were examined as a function of deposition/sputter etch (D/S) ratio, which was controlled by the bias power in HDP-CVD. FTIR spectra show that the positions of Si–O and Si–F peaks are independent of the bias power, but the Si–O shifted to a higher wave number and Si–F 2 appeared upon annealing for the films deposited at lower bias power. Stress hysteresis of the FSG films after the first thermal cycle shows a nonequilibrium nature of the microstructure related to impurity content, especially for the film deposited with lower bias power. Thermal desorption of H 2O, F, O 2 and Ar were examined, while most of the desorption behaviour can be related to the physical pore structure and pore quantity.

Generation of Bonding Structure Due to Organic Carbon and Organometallic Carbon as a Function of Gas Source

SiOC films with low dielectric properties were deposited by high density plasma chemical vapor deposition (CVD) using mixed source gases by considering of oxygen and bistrimethylsilylmethane. SiOC films can be divided into two bonding structures on the basis of the chemical shift according to the flow rate ratio: the cross-link and cross-link breakage structure. The chemical shift is determined as the result of the Diels–Alder reaction between a carbocation and a substituent group induced by both the resonance and inductive effects during the nucleophilic deposition reaction. The relative carbon content decreases as the oxygen flow rate increases, but the lowest dielectric constant of 2.1 was obtained for an annealed film with an organometallic carbon structure. The different bonding structures between organic carbon due to the dominant resonance and organometallic carbon due to the dominant inductive effect can be analyzed from FTIR and Raman spectra.

Effect of fluorine incorporation on silicon dioxide prepared by high density plasma chemical vapor deposition with SiH4∕O2∕NF3 chemistry

The effect of fluorine incorporation on properties of silicon dioxide thin films has been studied as a function of NF3∕O2 gas flow ratio. Fluorine was incorporated into silicon dioxide films during high density plasma chemical vapor deposition with the SiH4∕O2∕NF3∕He gas mixture used to improve the gap-filling ability for shallow trench isolation of devices. Refractive index measured by ellipsometry decreased with increasing NF3∕O2 flow ratios for both as-deposited and annealed films. X-ray reflectivity measurements showed that both fluorine incorporation and thermal annealing reduced the film density. The analysis of infrared absorption spectra showed the relaxation of the Si-O-Si bond with increasing NF3∕O2 flow ratios and thermal annealing. The secondary ion mass spectroscopy and x-ray photoelectron spectroscopy studies confirmed the behavior of fluorine diffusion and the binding energy for each species in the films, respectively. These results showed that through fluorine incorporation and thermal annealing, the network structures of silicon dioxide could be modified from low order rings to high order rings accompanied by the enlargement of nanovoids.

Alkylation of nanoporous silica thin films by high density plasma chemical vapor deposition of a-SiC:H

Film stacks of a-SiC:H and molecularly templated nanoporous silica thin films have been prepared, and alkylation of pore surfaces of the nanoporous silica layer by the a-SiC:H layer was studied. The a-SiC:H thin films were deposited by high-density plasma chemical vapor deposition (HDP-CVD) using trimethylsilane (3MS) as the precursor. Carbon is found to uniformly distribute in the thin nanoporous silica film, and the carbon content in the nanoporous film decreases with increasing the a-SiC:H deposition temperature. We used the modified Sanderson formalism to estimate the corresponding Si(2p) and C(1s) electron energies in x-ray photoelectron spectra (XPS) for possible terminal species on pore surfaces in the nanoporous silica layer. According to the XPS analysis and thermal desorption mass spectroscopy, the terminal species are probably in the chemical form of alkoxyl structures. The alkoxyl terminal groups introduced into the nanoporous silica thin film are believed to stem from hydrocarbons trapped in microvoids in the a-SiC:H film, which are formed during the HDP-CVD deposition. The terminal alkoxyl groups in the nanoporous silica layer can greatly enhance the hydrophobicity of the nanoporous silica dielectric, and hence improve the dielectric property of the film stack of a-SiC:H/nanoporous silica. An effective dielectric constant smaller than 1.7 can be obtained for the film stacks.

A Method for Fabricating a Superior Oxide/Nitride /Oxide Gate Stack

A superior oxide/nitride/oxide (ONO) gate stack was demonstrated. High density plasma chemical vapor deposition was used to deposit the silicon nitride layer instead of the conventional low-pressure chemical vapor deposition for silicon/oxide/nitride/oxide/ silicon technology. The densified nitride layer was performed by high-temperature dry oxidation to form a thermally grown blocking oxide layer on the silicon nitride rather than a deposited oxide layer. The ONO gate stack shows large memory window, high breakdown voltage, and reliable endurance characteristics, which is a potential candidate for future nonvolatile memory technology.

High density plasma chemical vapor deposition of diamond-like carbon films

This work was based on the studies of the influence of the plasma process on the characteristics of diamond-like carbon (DLC) films deposited by high density plasma chemical vapor deposition (HDP-CVD). DLC is a material that shows several good characteristics like high electrical resistivity, lower dielectric constant, high breakdown field, lower stress, high density, and hardness and chemical inertness. This material is important actually in mechanic, optic, and chemistry and mainly in microelectronic areas. For microelectronic process the best results were obtained by plasma of pure methane: low dielectric constant (1.7) and high resistivity 5×1013Ωcm.

Modeling gas-phase nucleation in inductively coupled silane-oxygen plasmas

A detailed chemical kinetics mechanism was developed to model silicon oxide clustering during high density plasma chemical vapor deposition of SiO2 films from silane-oxygen–argon mixtures. An inductively coupled plasma reactor was modeled in a one-dimensional multicomponent two-temperature framework. Spatial distributions of species concentrations were calculated. The effects of discharge parameters and the main processes contributing to cluster formation were examined. A sensitivity analysis was conducted to determine the dominant reactions that affect the model results.

FIELD EMISSION FROM NANOSTRUCTURE CARBON FILMS

We studied the field emission properties of carbon nanostructure, which comprised of high density carbon nanotips on Si. These carbon nanotips are grown on metal coated Si by a high density plasma chemical vapor deposition (HDPCVD) using an inductively coupled plasma. The emission current increases with increasing the growth temperature. They exhibited an emission current density of 1 mA/cm 2 at a field of 1.95 V /μ m when the growth temperature was 700°C. We developed high brightness field emission lamps using the carbon nanotips.

Characterization and reliability of low dielectric constant fluorosilicate glass and silicon rich oxide process for deep sub-micron device application

Fluorosilicate Glass (FSG) with low dielectric constant currently has been replaced as an alternative to SiO 2 for device speed improvement. However, several integration aspects, such as Fluorine (F) distribution, F thermal stability, gap fill capability, capacitance reduction and via resistance of FSG prepared by the high density plasma (HDP) chemical vapor deposition (CVD) method are of concern for sub-0.18-μm devices. In this study, HDP–FSG films show different F concentrations at different locations on an 8-inch wafer. In addition, the FSG film shows poor thermal stability and F diffuses out of the film after high temperature annealing and the pressure cook test (PCT). However, the thermal stability of FSG film can be improved by capping with an oxide layer. The results indicate that silicon rich oxide (SRO) has a better effect at blocking the F diffusion out of FSG films at high temperature than plasma enhanced oxide (PE-OX). For the gap fill capability, HDP-FSG can fill all 0.23-μm gaps and some of the 0.21-μm gaps with an aspect ratio <3.8 but not the 0.19-μm gaps. A 8000 Å HDP–FSG film with 600 Å USG liner and 2000 Å cap layer shows approximately 7.5 to 7.7% capacitance reduction on 0.23/0.23-μm gaps when compared with USG (undoped silicate glass). In addition, FSG has a larger capacitance reduction on the wider metal lines than the thinner metal lines at the same gap size due to a capacitance fringe effect. The via resistance for 0.26 μm unlanded via (which allow minor photo mis-alignment) of HDP-FSG film is also similar to that of USG.

The interface of fluorinated amorphous carbon with copper metallization

We have studied fluorinated amorphous carbon (a-F:C) films, prepared by High Density Plasma Chemical Vapor Deposition (HDP-CVD) methods from CH 4 and C 4F 8, as candidates for low- k inter metal dielectric (IMD) applications. In order to enhance the film's adhesion to the adjacent layers, an adhesion promoter layer was introduced. The samples used for the current research consist of a metal layer (Cu or its diffusion barriers Ta or TaN) and the a-F:C film, with the adhesion promoter sandwiched in between. In order to learn about the film and interfaces stability the samples were annealed at 400 and 500°C for 30 min. Up to 400°C, no metal diffusion into the adhesion promoter was observed. After 30 min of 500°C annealing, no Cu outdiffusion was observed by XPS nor was a change in the Cu2p transition peak's form suggesting that no serious chemical reaction has occurred at the interface. No major Cu diffusion was detected by RBS but SIMS measurements have showed Cu diffusion into the adhesion promoter after 500°C annealing, 30 min. The dielectric constant of the film is ∼2.7 (measured by C– V at 1 MHz) after 400°C annealing and much higher after 500°C annealing. The results obtained so far show that the integration of a-F:C as IMD is possible but there are some problems to be solved.

Novel plasma chemical vapor deposition method of carbon nanotubes at low temperature for field emission display application

We developed a novel growth method of aligned carbon nanotubes. A high density plasma chemical vapor deposition (PECVD) has been employed to grow high-quality carbon nanotubes (CNTs) at low temperatures. High-density, aligned CNTs can be grown on Si and glass substrates. The CNTs were selectively-deposited on the patterned Ni catalyst layer, which was sputtered on Si. The CNTs exhibited a turn-on field of 0.9 V/μm and an emission current of 480 μA/cm2 at a field of 3 V/μm.

Deposition temperature effects of high density plasma chemical vapor deposition films for subquarter micron devices application

A detailed study for the high density plasma chemical vapor deposition (HDP-CVD) process was presented to prevent metal distortion issues and metal corrosion risk. The deposition temperature increased and then saturated as the film deposited, based on the correlation of wet-etch rate and deposition temperature. The stress of HDP-CVD film also trended up, but the deposition rate decreased. Lowering of the deposition temperature of HDP-CVD film was key to preventing the metal distortion. A two-step deposition recipe with 10 s Ar cooldown was developed to solve the metal distortion issue on subquarter micron devices.

Stress Behavior of High Density Plasma Chemical Vapor Deposition Oxide Deposited on a Metal-Patterned Wafer

A high density plasma chemical vapor deposition (HDPCVD) oxide was used as an inter metal dielectric (IMD) due to its good gap-fill properties for compensating the tensile stress of Al metal layers. When the HDPCVD oxide was deposited on a metal patterned wafer, however, the oxide showed tensile stress. In order to understand the mechanism of the characteristic stress behavior of the HDPCVD oxide on a metal patterned wafer, the change in magnitude of the wafer bow was measured as a function of oxide thickness, and was modeled quantitatively using the density of metal patterns and the stress change of the metal film. In the model, the oxide deposited between metal lines was assumed to have tensile stress due to the relatively high shrinkage of the neighboring metal pattern. When the deposited HDPCVD oxide thickness was thinner than that of the metal film, only the stress of the lower parts of the metal film, which was connected to the oxide, could affect the change of the wafer bow value. When the deposited oxide thickness was greater than that of the metal film, the stress of the oxide above the metal film was assumed to be compressive. Using the above assumptions and a simple mathematical model, the change in magnitude of the wafer bow was calculated and compared with experimental results. The calculated data were in good agreement with the experimental values.

Control of Plasma Damage to Gate Oxide during High Density Plasma Chemical Vapor Deposition

Gate oxide damage resulting from high density plasma chemical vapor deposition of silicon oxide was investigated using damage sensitive antenna structures with area ratios up to 200,000:1. Significant damage was detected from an unoptimized oxide deposition process. A 24−1 fractional factorial experimental design was used to screen the effect of four parameters: radio frequency power, microwave power, electrostatic chuck potential, and magnetic field. RF power and electrostatic chuck potential made no contribution to oxide degradation. The main factor was microwave power, and further experiments with microwave power ranging from 1500 to 2500 W showed that gate charging damage increased with microwave power, with the extent and distribution of damage depending on the magnetic field shape.