Temperature controlled laser chemical vapor deposition (LCVD) using thermal imaging

To describe the thermal imaging control system used to deposit lines of graphite in a laser chemical vapor deposition (LCVD) system.

A thermal imaging‐based control system is applied to the LCVD process to deposit layered carbon lines of uniform height and width. A 100 W CO₂ laser focused to a 200 μm diameter spot size is used to provide the heat source for the carbon deposition. A high resolution thermal imaging camera is used to monitor and control the average deposition temperature.

Carbon lines are grown with heights of 250 μm and widths of 170 μm consisting of 20 layers. Laser spot temperatures are in excess of 2,170°C, and the total pressure used is 1 atm with a 75 percent methane concentration and the remainder hydrogen. The length of the lines is 3.3 mm, and the scan speed is 5 mm/min. The volumetric deposition rate is 0.648 mm³/h.

The temperature process control resulted in uniform geometry at the center of the lines, but it was not as effective at the ends of the lines where the geometry was more complex.

Introduces a control technique for uniform line deposition for the LCVD process, which represents a core building block for complex geometries. The establishment of basic control algorithms will enable LCVD to realize the potential for rapid prototyping of metals and ceramics with sub‐millimeter feature sizes.