Traditionally, lead has been the product of choice for radiation shielding. Tungsten shielding blanket has the ability to field-fit, providing for attenuation of radiation totaling from 5 to 10 person-Rem/years than provided by the equivalent weight of traditional lead blanket. And since tungsten alloy is thinner and weighs as much as 50 percent less than lead, it may be more forgiving when workers are performing the physical activities required in a nuclear power plant.

With the same density, tungsten blanket has the similar thickness than lead blankets. And highly flexible and can be molded or formed into any shape. It often competitively priced to lead alternatives. It will engineer and fabricate specialized profiles, slabs and ribbon, including lockable "High Rad" applications.

Here, the method described above has an effect of preventing direct reaction of Ti and WF.sub.6 when an adhesion layer is a laminated layer of Ti/TiN films and a tungsten shielding blanket is formed on the adhesion layer. A direct reaction of Ti and WF.sub.6 will form a solid substrate which will exhibit a volume expansion and become a cause of peeling-off of a layer.

When an adhesion layer for forming a tungsten shielding blanket is formed by sputtering, the substrate is often fixed on a mount using a holder or hooks. At portions under these hooks, a SiO.sub.2 film which is an inter-layer insulating layer is exposed because almost no film is formed under the hooks by sputtering. When a tungsten shielding blanket grows on the exposed SiO.sub.2, the tungsten shielding blanket is easily peeled off because of weak adhesion anti particles are produced.

Description of Tungsten Blanket

Normally, as a plug for connecting wiring layers of multiple layer wiring, tungsten which is a refractory metal has been employed. However, tungsten alloy has a weak adhesion with SiO.sub.2. Thus, for forming tungsten blanket on an inter-layer insulating film formed of SiO.sub.2, laminated adhesion layer of titanium Film is formed first and then tungsten blanket is formed thereon.

Tungsten Blanket Deposition

Tungsten blanket deposition apparatus comprises a reactor the inside of which is evacuatable, a gas inlet means for introducing a reaction gas into the reactor, mount means for mounting an object substrate to be treated, penetration-preventing means for preventing penetration of gas, disposed to cover a peripheral portion of a surface of the object substrate to be treated and having an inner diameter smaller than a diameter of the object substrate and an outer perimeter larger than that of the object substrate, and another gas inlet means for introducing a gas to a space on the periphery of the object substrate covered by the penetration-preventing means. Growth of blanket tungsten on a peripheral SiO.sub.2 portion of substrate is prevented and hence production of particles caused by peeling-off of tungsten blanket is prevented.

To prevent a growth of tungsten blanket on the exposed SiO.sub.2 film, the exposed SiO.sub.2 film around the substrate is covered with a ring for preventing reaction gas from reaching the exposed film of SiO.sub.2.
In the prior art method of forming tungsten blanket described above, when a gas of SiH.sub.4 or SiH.sub.2 Cl.sub.2 is allowed to flow on a surface of a substrate for forming thereon a thin film of silicon, it is not supplied on the portion covered by a ring for preventing penetration of reaction gas. Thus, a layer of SiO.sub.2 is exposed on a periphery of the substrate.
In the next process of forming WSi film by providing a flow of WF.sub.6 gas, WF.sub.6 may penetrate into a portion where SiO.sub.2 film is exposed on a periphery of the substrate. In this case, tungsten blanket grows directly on the SiO.sub.2 film, and results in a production of particles.

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