Silicon dioxide, phosphorus-doped

The hazards associated with phosphorus-doped silicon dioxide passivations are now widely recognised and manufacturers have accordingly adopted control limits of 2-4% by weight of phosphorus. A few manufacturers are also making use of alternative forms of passivation layers, the three most popular of which are ... 

Silicon nitride has received the most attention, but only a few manufacturers are using it commercially because it is difficult to control some of the properties which can affect the operation of an IC (such as hydrogen content and stress). The main attribute of silicon nitride is that it is impervious to moisture and this makes it the ideal passivation when highly phosphorus-doped silicon dioxide layers are used to separate two levels of interconnection, as, for example, in gate arrays. (One requirement of an inter-layer dielectric is that it should smooth out underlying steps, and 6-10% phosphorus-doped silicon dioxide has the appropriate flow properties to do this.) In such a case silicon nitride prevents the uniform cathodic corrosion which is associated with the use of such oxide layers as passivations. 

Semiconductor microchip processing often involves chemical vapor deposition (CVD) of thin layers. The material being deposited needs to have certain desirable properties. For instance, to overlay on aluminum or other bases, a phosphorus pentoxide-doped silicon dioxide coating is deposited as passivation (protective) coating, by the simultaneous reactions... 

Silicon dioxide films have been an essential factor in the manufacture of integrated circuits from the earliest days of the industry. They have been used as a final passivation film to protect against scratches and to getter mobile ion impurities (when doped with phosphorus). Another application has been as an interlayer dielectric between the gate polysilicon and the aluminum metal-ization. Initially, most such films were deposited in atmospheric pressure systems. In recent years, low pressure processes have assumed greater importance. We will begin by examining the atmospheric process. 

Earlier, we reviewed silicon dioxide (thermal) films deposited with added phosphorus to serve as a getter for mobile ion impurities, as a final passivation film. Plasma-enhanced silicon nitride can also be doped with phosphorus.6 Some of the film characteristics have been reviewed, and it was found that the films with 2 to 3% P had the best electrical quality. No measurements of stress or H2 content were reported, so it is not clear that these would be use-able films. 

Silicon Dioxide Etchiiig Doping by phosphorus Diffusion... 

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