Pulsed laser deposition of laterally graded X-ray optical multilayers on substrates of technical relevance

Pulsed Laser Deposition (PLD) is used for the preparation of Ni/C, W/C, and Mo/Si multilayers having X-ray optical quality. For the synthesis of layer stacks involving a uniform or a graded thickness distribution across 4"-wafers the conventional thin film deposition equipment of PLD has been modified. This modification provides a precise spatial control of the plasma plume orientation in the deposition chamber. With this arrangement the emission characteristic of the plasma source can be computer controlled and the desired coating profile can be tailored across an extended substrate via a stepper-motor-driven target manipulator. Thus, e.g., film thickness uniformity (Delta t(ind s)smaller than 2%) is obtained on substrates up to 4" diameter even for smaller target-substrate distances. For laterally graded Ni and individual layers linear thickness gradients of dt(ind s)/dx = 3.2 x 10(exp-8) were confirmed over the total substrate length by spectroscopic ellipsometry. The parameters ded uced from single layer deposition were applied for the synthesis of laterally graded Ni/C multilayers. A mean value of the gradient of the stack period thickness dt/dx = 6.2 x 10(exp-8) confirmed by X-ray reflectometry (nominal value dt(ind 0)/dx = 6.4 x 10(exp-8)) characterises precision and reproducibility of the coating process.