Haruki Komano

Beam induced deposition of an ultraviolet transparent silicon oxide film by focused gallium ion beam

We have deposited a silicon oxide (SiOx) film with a high optical transmittance in the DUV region by a focused ion beam induced deposition technique using a gallium ion beam and a mixture of oxygen and TMCTS(1,3,5,7‐tetramethylcyclotetrasiloxane) as a source gas. The optical transmittance of a 0.3 μm thick film is higher than 90% at the wavelength of 250 nm. The transmittance of the deposited SiOx film depends on both the source gas and ion beam irradiation conditions. A scaling to explain the transmittance along with the ion beam conditions is proposed.

A rewiring technique for integrated circuit operation analysis using a silicon oxide film deposited by a focused ion beam

The silicon oxide deposition technique with a Si focused ion beam was applied to rewiring from the first aluminum line below a wide power line in a 256k CMOS SRAM. The widths of the power line and the first aluminum line were 130 and 1.5 μm, respectively. First, the layer on the first aluminum line was etched for an area of 4.5×4.5 μm by a Ga focused ion beam. Second, silicon oxide was deposited into the hole using a 60‐keV Si2+ focused ion beam with a mixed gas of tetramethoxysilane and oxygen, then, the deposited silicon oxide film was etched for an area of 2×2 μm down to the first aluminum line by the Ga focused ion beam. Last, tungsten was deposited for rewiring from the first aluminum line using the conventional focused ion beam method. The leak current measured between the deposited tungsten and the power line was 1×10−8 A at 5 V which is sufficiently small for operation analyses of semiconductor devices.

Silicon Oxide Film Formation by Focused Ion Beam (FIB)-Assisted Deposition

A silicon oxide film has been formed by means of 60 keV Si2+ focused ion beam (FIB)-assisted deposition. A mixture of tetramethoxysilane (Si(OCH3)4) and oxygen gases was blown onto a sample surface through a 0.2-mm-inner-diameter nozzle. A gold, silicon, and beryllium alloy source was used to produce a Si2+ ion beam in the FIB system. The beam diameter and current were 0.3 µm and 0.1 nA, respectively. The deposited film with 0.1-µm thickness and 0.7-µm width consisted mainly of silicon and oxygen, and contained scarcely any carbon. The relative ratios of silicon to oxygen atomic concentration were 1:2 near the film surface and 1:1 inside the film. The resistivity of the deposited film was 2.5 MΩcm at 5 V, and the breakdown voltage was 40 V. It was found that it would be possible to use the deposited film as an insulator for integrated circuit repair in developing semiconductor devices.

A study of radiation damage in SiN and SiC mask membranes

Radiation damage in SiN and SiC films prepared by low‐pressure chemical vapor deposition (LPCVD) is reported. A pattern placement error of 0.05 μm at the edge of the x‐ray radiation area was introduced for SiN membranes by a radiation dose of 12 kJ/cm2. The electron spin resonance (ESR) signals with a g value of 2.004, which was attributed to the Si–N dangling bond, were observed. Both the error and the spin density increased with increasing radiation dose up to 12 kJ/cm2 and remained constant thereafter. The error was explained as the result of Si–N bond scission caused by x‐ray radiation, leading to tensile stress relaxation in the radiated area. In the case of SiC films, a pattern placement error was less than a detection limit of 0.03 μm for a radiation dose of 10 kJ/cm2. ESR signals with a g value of 2.003, being attributed to the Si–C dangling bond, were observed. However, the spin density in this case did not change by radiation up to 20 kJ/cm2. It is inferred that the LPCVD SiC membrane is damage ...

Focused Ion Beam Assisted Etching of Quartz in XeF2 without Transmittance Reduction for Phase Shifting Mask Repair

Focused ion beam (FIB) assisted etching of quartz by a Ga FIB and XeF2 gas was studied for the purpose of avoiding the transmittance reduction by a Ga FIB. Transmittance was above 99% with the existence of XeF2 to the extent that the etching yield was more than 1.7 times larger than that of sputtering. It was also found that postetching above 15 nm by a Ga FIB and XeF2 gas after the Ga ion implantation recovered the transmittance. These techniques will be applied to repairing phase shifting masks without transmittance reduction.

The Effects of HCl Added to Chemical Vapor Deposition Source Gases for Producing a SiC X-Ray Mask Membrane

The effects of adding HCl to the chemical vapor deposition source gases on the stress, optical transparency, and surface roughness of a SiC X-ray mask membrane were examined. It was found that the stress dependence on the source gas carbon-to-silicon ratio was changed by adding HCl, and that a SiC membrane with low stress and high optical transparency is obtainable by adjusting these parameters. The surface roughness was about 15 nm from peak to valley under a good condition. The X-ray diffraction results of the SiC membranes showed that the peak sharpness, which indicates the crystal qualities such as densities of various intrinsic defects and the size of each crystal grain, is related to the optical transparency, and that the crystal orientation parameter is related to the surface roughness.

Silicon oxide deposition using a gallium-focused ion beam

Experiments concerning silicon oxide deposition using a focused ion beam were carried out in order to apply silicon oxide as insulator in integrated circuit modification. Silicon oxide film was formed using a 25-keV gallium focused ion beam with a mixed gas of 1.3.5.7- tetramethylcyclotetrasiloxane and oxygen. The deposited film consisted of mainly silicon and oxygen, which was analyzed by micro-Auger electron spectroscopy. It also contained 5 percent gallium, but carbon content was below noise level. The ratio of silicon to oxygen was 1 to 2. It was found that carbon content depended on oxygen used as deposition source gas. The resistivities of the eight deposited silicon oxide films were measured. The resistivities wer 28-79 M(Omega) cm at 5 volts and these values did not change significantly even after the samples were left in a room for three months. It was determined that it will be possible to use deposited silicon oxide for integrated circuit modification.

Focused ion-beam imaging of defects on deep-UV single-layer halftone masks

At the first stage of defect repair on masks with focused ion beam (FIB), it is necessary to recognize defects by imaging. One of the problems in halftone mask imaging by FIB is that the contrast between halftone (HT) film and quartz (Qz) substrate is not sufficient to recognize material. We investigated the methods of the defect area distinction in deep UV silicon nitride (SiNx) single-layer halftone masks to avoid the transmittance decrease of masks induced by FIB irradiation. The cause of the difficulty in the area distinction is that the difference between the mean secondary electron intensity of HT area and that of Qz area is small in comparison with the width of the secondary electron intensity distributions. A conventional filter was found to be effective to narrow the intensity distributions and the area of defects on halftone masks could be recognized by means of the image filter in the images obtained with a low FIB dose.

Divot defect repair on a deep ultraviolet SiNx halftone mask

Divot defect repair on deep ultraviolet SiNx halftone masks in the case of 0.275 μm (on a wafer) line and space patterns was investigated experimentally. The problem regarding imaging is the difficulty of area recognition due to low contrast of halftone masks without the focused ion beam (FIB) irradiation damage. It is overcome by means of limiting the total FIB dose for imaging and by means of image processing with an image filter. Opaque carbon (C) film deposition on a divot defect was found to improve the performance of a defective area. The degree of the improvement was not perfect but allowable for practical use. It was also found that there were other factors that make the performance of the repaired area worse than the nondefective area, except for missing of the phase shift effect.

Improvement in Optical Transparency of SiC Membrane by Modulating Source Gas Ratio in Chemical Vapor Deposition

A method to improve the optical transparency of a SiC membrane is studied by modulating the source gas carbon-to-silicon ratio (C/Si) during chemical vapor deposition. As a result of an investigation conducted under different C/Si conditions, the optical transparency was found to be highest at C/Si=0.9. Optical transparency decreased at lower C/Si probably due to the increase of surface roughness, and at higher C/Si due to the degradation of crystal quality. By alternate deposition under the condition of C/Si=0.8 and 0.95, the SiC membrane with an optical transparency of 68% was obtained without applying an antireflection coating.