Seok-Min Yun

The deposition of SiOF film with low dielectric constant in a helicon plasma source

SiOF films deposited by a helicon wave plasma chemical vapor deposition method has been characterized using Fourier transform infrared spectroscopy and ellipsometry. High density plasma of ≳1012 cm−3 can be obtained on a substrate at low pressure (<10 mTorr) with rf power ≳400 W with a helicon plasma source. A gas mixture of SiF4, O2, and Ar was used to deposit SiOF films on 5 in. Si(100) wafers not intentionally heated. Optical emission spectroscopy was used to study the relation between the relative densities of the radicals and the deposition mechanism. It was found that the addition of Ar gas to the SiF4/O2 mixture greatly increased the F concentration in the SiOF film. Discharge conditions such as gas composition, sheath potential, and the relative densities of the radicals affect the properties of the film. The dielectric constant of the SiOF film deposited using the helicon plasma source was 3.1, a value lower than that of the oxide film by other methods.

Frequency dependence of helicon wave plasmas near lower hybrid resonance frequency

The frequency dependence of helicon wave plasmas has been studied at 1–25 MHz of rf power, and at magnetic fields of 200–1150 G using various gases. Maxima in the electron density occur for particular frequencies at each magnetic field. These optimum frequencies are propor-tional to magnetic field strength and inversely proportional to the discharge gas mass. The exist-ence of optimum frequencies in each magnetic field and gas mass indicates the possibility of lower hybridresonance heating effect. The experimental optimum frequencies are slightly lower than the theoretical lower hybrid resonance frequencies. The difference between the two frequencies can be explained by the Doppler shift effect.

Low dielectric constant CF/SiOF composite film deposition in a helicon plasma reactor

Abstract Low dielectric constant CF/SiOF composite films are deposited using tri-ethoxy-fluorosilane (FTES) and O 2 mixture in a helicon plasma reactor without intentional heating or biasing the substrate. Optical emission spectroscopy (OES) is used to study the relation between the relative densities of the radicals and the film properties. The OES data imply that the FTES and O 2 gases are greatly dissociated above the RF power of 900 W. Consequently, the deposition process of helicon plasma CVD where the source gases dissociated highly form CF/SiOF composite film is different from thermal CVD where the gases react chemically on the substrate and make the SiOF film. FTIR and XPS spectra show that the film has Si–F, Si–O, and C–F bonds. The Si–F and C–F bonds may lower the dielectric constant greatly. As the O 2 /FTES ratio decreases, the fluorine concentration increases and the dielectric constant decreases.

Control of plasma parameters by using noble gas admixtures

Electron temperature and density in pure He, Ar, and Xe plasmas are estimated by zero-dimensional particle and power balance equations and measured by a Langmuir probe. Both of the modeling and experimental results show that the He (Xe) plasma has the highest (lowest) electron temperature and lowest (highest) electron density for a given fill pressure and source power. We find that the electron temperature is weakly dependent on the rf power, and thus the electron density can be controlled using the rf power. The electron temperature and density are also modeled and measured in mixtures of two noble gas species. We find that the electron temperature can be controlled by altering the composition of the noble gas mixture. Thus modulation of noble gas admixture ratios and rf power allows the electron density and temperature to be controlled independently. This independent control is shown to maintained with the addition of up to 20% partial pressure of oxygen, suggesting binary noble gas admixtures may provi...

A Study on Low Dielectric Material Deposition Using a Helicon Plasma Source

Characteristics of SiOF films deposited by a helicon plasma source have been investigated using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and ellipsometry. High density Ar plasma of >10 12 cm -3 was obtained on a substrate at low pressure ( 400 W using a helicon plasma source. The effect of the RF power, the magnetic field strength, and the pressure on the helicon wave for high density plasma has been studied. A gas mixture of SiF 4 , O 2 , and Ar was used to deposit SiOF film on 5 in. (100) Si wafers not intentionally heated. Optical emission spectroscopy was used to study the relation between the relative densities of the radicals and the deposition mechanism. The effects of the RF power, the gas composition, and the Ar addition to the SiF 4 /O 2 mixture on the plasma-phase composition and on the properties of the film, have been studied. Discharge conditions such as gas composition, sheath potential, and relative densities of the radicals affect the properties of the film. The dielectric constant of the SiOF film deposited using the helicon plasma source was 3.1, a value lower than that of the oxide films obtained using other methods.

Radial density profile change near lower hybrid frequency in M = 0 helicon wave plasmas

Abstract Radial density profiles are measured near the lower hybrid frequencies with various magnetic fields and frequencies in m = 0 mode helicon wave plasmas. Abrupt radial density changes occur near the lower hybrid frequency where the electron density is higher. Experiments under various conditions such as various magnetic fields and gases show that these phenomena occur near the lower hybrid frequencies.

Electrical characteristics of helicon wave plasmas

The external electrical characteristics of helicon wave plasmas have been studied over a wide range of magnetic fields, radio frequency (RF) power, frequencies, and Ar gas pressures. External parameters, such as antenna voltage, current, and phase shifts, and internal parameters, such as electron density, are measured. The equivalent discharge resistance, reactance, and power transfer efficiency are calculated through these measurements. The characteristics of helicon mode is compared with inductively coupled plasma (ICP) and low mode. The power efficiency of the helicon mode is better than that of other modes. Consequently, electron density of helicon mode is much higher than that of other modes. This means the existence of a mechanism where electrons are very efficiently accelerated by the electric field of the antenna in the helicon mode. The power efficiency of helicon mode is higher at lower RF frequency and at optimum gas pressure than that of other modes.

SiOF Film Deposition Using FSi ( OC 2 H 5 ) 3 Gas in a Helicon Plasma Source

SiOF film deposited using FSi(OC 2 H 5 ) 3 (known as FTES) and O 2 mixture in a helicon plasma source is characterized with various plasma conditions. High density O 2 /FTES/Ar plasma above 10 12 cm -3 is obtained at low pressure (<3 mTorr) with rf power above 900 W in the helicon plasma source. The plasma parameters such as electron density with the various rf power, the magnetic field strength, and the pressure are measured. A gas mixture of FTES and O 2 is used to deposit SiOF film on 5 in. Si(100) wafers without intentional heating or biasing the substrate. Optical emission spectroscopy (OES) is used to study the relation between the relative densities of the radicals and the film properties. The OES data imply that the FTES and O 2 gases are greatly dissociated at the helicon mode, which is launched above theshold plasma density. Thus, the SiOF film deposited in the helicon reactor contains C-F bonds which are not sound in the SiOF film made by thermal chemical vapor deposition, where the FTES and O 2 react chemically on the substrate. Fourier transform infrared and X-ray photoelectron spectroscopy spectra show that the film has Si-F, Si-O, and C-F bonds. The Si-F and C-F bonds may lower the dielectric constant greatly. As O 2 /FTES ratio decreases, the fluorine concentration increases and the dielectric constant decreases.

M = + 1 MODE HELICON WAVE EXCITATION USING SOLENOID ANTENNA

Abstract In most helicon wave experiments, there has been a poor agreement between the theoretical wave power deposition and the plasma density radial profiles. The characteristics of the solenoid antenna employed for the excitation of m = 1 mode helicon waves are investigated. A cylindrical high density plasma column with high intensity ArII emission is observed to be of a cylindrical shell shape. In cross section, the location of the high intensity column nearly coincides with the maximum point of wave power deposition. The wave magnetic field radial profiles agree well with computations. These results show an excellent agreement between the theory and density profile produced by the m = 1 helicon wave.

LOW-DIELECTRIC-CONSTANT-FILM DEPOSITION WITH VARIOUS GASES IN A HELICON PLASMA REACTOR

Low-dielectric-constant SiOF films are deposited using O2/SiF4 and O2/FSi(OC2H5)3 mixtures in a helicon plasma reactor, and good quality films can be obtained without intentional heating or biasing of the substrate. Optical emission spectroscopy (OES) is used to study the relation between the relative densities of the radicals and the film properties. The OES data imply that the source gases are highly dissociated above the RF power of 900 W where the helicon mode is generated. Consequently, the mechanism of helicon plasma chemical vapor deposition (CVD) is different from that of thermal CVD. In the case of thermal CVD, the source gases react chemically on the high-temperature substrate and form films. However, in the case of helicon wave plasma CVD, the source gases are highly dissociated in the high-density plasma and many radicals are produced, that react on the substrate. SiOF films are made in the case of O2/SiF4 but CF/SiOF composite films are made in the case of O2/FSi(OC2H5)3, where FSi(OC2H5)3 is highly dissociated in plasma and C participates in the film formation. Films with a low dielectric constant of below 3.0 can be made.