The Secon passivation technology offers a short additional process in the etch chamber. The elements will be passivated immediately after the etch step without breaking the vacuum. The additional time required is < 10% of the whole process.

Two options are available: -

• Passivation by an amorphous silicon layer for selective (at the open junction only) passivation for low temperature applications
• passivation by silicon nitride for high temperature applications

The deposition process uses for the generation of Si₃N₄ nitrogen radicals, obtained from N₂ dissociation in the "high density" microwave plasma of the Secon XRG-800 radical generator. This patented radical generator is - due to its principle of construction - able to provide the necessary high energies for the dissociation of nitrogen. Thus it is possible to cease using ammonia for generating highly reactive nitrogen. Using ammonia brings a number of disadvantages, e.g. an increased binding of hydrogen to silicon.

The nitrogen radicals react on the substrate surface with the dissipating (Silane) SiH₄ to Si₃N₄. This surface reaction is reached by the surface temperature which, depending on the technological requirements, is between 250 and 380 ºC, and is reached by the high frequency supplied via the RIE-electrode. With this process, excellent dense Si₃N₄ layers can be deposited.

Advantages compare to conventional plasma: -

• Hydrogen Content: With its 8-10 atomic percent not only lower, but also the bonding of hydrogen is predominantly uncritical to the inert nitrogen, as seen in the IR spectrum. Bonding of hydrogen onto Si creates more problems via the reactivity with water. This property can be optimized through choice of process temperature.
• Compressive stress: Correlates directly with the hydrogen content and  the deposition temperature. Lower than in conventional plasma deposited layers
• Layer Thickness: Theoretically unlimited, depends on the deposition speed and the area to be deposited. Typical value between 1 and 2 µm to obtain sufficiently dense layers

• Rate: Approximately 600nm/min

• Temperature Stability: > 1000 ºC, determined by blocking tests with water.
• Layer Density: Correlating with the layer thickness. Wet etch tests showed sufficient density at layer thickness between 300 and 400 nm. Leakage emanates from pinholes,  which cannot penetrate the total layer at these thickness.
• Adherence: Correlates directly with t he deposition temperature. At the said temperature, an adherence superior to those of layers obtained with conventional plasma, was obtained.

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Last modified: Juli 03, 2002