Pat. No. 3117687
Pat. No. 3664472
Pat. No. 3954938
US 6858263 B2
Superiority of coating by plasma-enhanced CVD technique
Film deposition using plasma-enhanced CVD includes two types: PVD (physical vapor deposition) and CVD (chemical vapor deposition). In PVD, the film deposition material is vaporized for deposition on the substrate, which is solidified again. One representative method is sputtering, in which ions are brought in to collide with the material to use the impact to eject the atoms. This gives the atoms orientation, which hinders uniform deposition of the material on the hole’s inner wall.
Meanwhile, CVD uses chemical reaction for decomposing the deposition material for depositing and solidifying on the substrate. Plasma-enhanced CVD makes use of discharge plasma to accelerate decomposition. Accordingly, deposition takes place in a gaseous atmosphere, which allows uniform deposition on the hole’s inner wall.
|Deposition method||PVD Platinum target||CVD Osmium vapor atmosphere|
|Characteristics||The film formed is crystalline, which makes it prone to the shape effect of particles, causing an edge effect. Uniform film deposition on the inner wall is difficult.||Osmium particles are small and the film formed has a very smooth surface. CVD offers high circularity, which allows a uniform film to be deposited even on the inner wall.|
Effect of osmium coating
Example of use on aperture plates for electron microscopes
The following illustrates the effects produced by osmium films deposited on aperture plates.
Charge-up prevention effect
Example) FE-TEM CL aperture
(TEM fluorescent screen spot image)
Beam damage mitigation effect
Example) FE-SEM blanking aperture
(Image of aperture after periodic replacement)
Actual results of osmium coating
Here are some examples of osmium deposition.
Osmium films deposited are very thin: about 10 to 100nm.
Coating on pipe inside
Osmium deposition allows high aspect ratio film deposition with our proprietary technology. The aspect ratio can be as high as 7 times. The sample image shows a pipe of 2 mm in diameter and 14 mm in length cut in half. This shows a mostly uniform film deposited on the inner wall.
Basically, any conductive material that does not contaminate vacuum can be used for film deposition.
|Examples of conductive materials||Tantalum, molybdenum, platinum, gold, titanium, stainless steel, tungsten, aluminum, copper, and silicon wafer|
Some nonconductive materials may be used for film deposition by using a special method.
|Examples of nonconductive materials||Resin and glass|
Osmium is a blue-gray rare metal of the platinum family. Its specific gravity is the highest of all elements at 22.57, melting point is 3045°C, and boiling point is over 5000°C. It has a hexagonal close-packed structure, which makes it stable at normal temperature and normal pressure.
Characteristics of osmium
Osmium is a metal with a melting point as high as that of tungsten. It is characterized by relatively high electrical conductivity for a rare metal at 11.4 and very high hardness with a Mohs hardness of 8.