Interfacial reactions and thermal stability of ultrahigh vacuum deposited multilayered Mo/Si structures

Because it allows the production of substantial quantities of large area, uniformly shaped substrates of normalGaP , the Liquid Encapsulated Czochralski technique is a major advance in normalGaP technology. Successful growth of single‐crystal ingots requires maintenance of visibility of the growth interface. This is accomplished by baking out the B2O3 encapsulant before use, tightly packing the polycrystalline normalGaP charge into the bottom of the crucible before growth, locating the center of heat at the bottom of the crucible, and keeping the B2O3 relatively hot during growth. The resulting ingots have uniformly high Hall mobilities, generally being at least as high as those reported for normalGaP grown by other techniques. The central regions of the ingots have dislocation densities ≤1×105 cm−2 . Effective distribution coefficients for S, Se, Te, and Zn have been found to be 0.23±0.08,0.16±0.05,0.012±0.003,normaland 0.096±0.05 , respectively.

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This paper presents high-temperature effects on CoSi2/polycrystalline silicon (poly-Si) bilayers, intended for metal-oxide-semiconductor gate applications. Both rapid thermal annealing and conventional furnace annealing were utilized for the investigation. At temperatures above 700 °C the structure breaks down due to silicon recrystallization within the silicide and simultaneous silicide growth into the polycrystalline silicon film. Recrystallized silicon adopts the silicide texture and this process terminates when the entire polysilicon layer is consumed. After completion the layer configuration is inverted, i.e., the silicide is adjacent to the gate oxide and covered with elemental silicon at the surface. This surface layer consists of large grains with few crystal defects, very different from the columnar structure of the as-deposited silicon. With further annealing, grain growth in both phases continues, and each grain will ultimately extend from the oxide interface to the free surface. Lateral grain dimensions are typically a few times the total film thickness at this stage. Silicon recrystallization in the silicide layer can be suppressed if the polysilicon is doped with phosphorus prior to metal deposition, or the phenomenon can be alleviated by an arsenic or boron implantation into the silicide.