Processing and control of selective area laser deposition from methane and hydrogen

The goal of this dissertation was to build a process machine that could be used to develop selective area laser deposition (SALD) into a process for solid freeform fabrication (SFF). SFF refers to manufacturing processes that fabricate parts using additive materials processing without part specific tooling or human intervention from solid model part descriptions. A secondary goal was to incorporate into this machine the ability to deposit diamond via chemical vapor deposition and to combine the chemistry necessary to deposit diamond with SALD to attempt selective deposition of {dollar}spsp3{dollar} bonded carbon.; A remote plasma computer controlled selective area laser deposition system is defined, designed, and fabricated. The computer controlled process variables included CH{dollar}sb4{dollar}, H{dollar}sb2{dollar}, O{dollar}sb2{dollar}, and Ar flow rates, process pressure, substrate temperature, microwave coupled power and impedance matching, laser power, and beam position and scan velocity. The process data files are derived from industry standard "STL" files and are preprocessed by two command line executed filters to create the data files for the process control program.; Deposition substrates included {dollar}rm Alsb2Osb3{dollar} and SiC powder, hot pressed BN, and Si wafers. Significant process parameters affecting the rate and quality of material formation are described. Laser scanning induced morphological instability is greatly reduced using new laser scanning subsystem that tightly integrates laser power and beam steering under single computer control. A microwave plasma subsystem was also used to deposit diamond from methane, hydrogen, and oxygen source gases. The microwave plasma subsystem was experimentally analyzed for use as a remote plasma free radical source for SALD using mass spectroscopy measurements of ethane production from remotely injected methane. It indicated that the yield of atomic hydrogen at the laser scanning site remained quite low under the best evaluated process parameters.; Si wafer substrates are susceptible to severe warpage and wafer cracking when used for SALD. A wafer thickness of 0.001 m, 800-1000{dollar}spcirc{dollar}C substrate bias temperatures, and higher laser scan velocities at constant laser fluence decreased the severity of warpage and incidence of cracking compared to 350-660 {dollar}mu{dollar}m thick wafers, 500-700{dollar}spcirc{dollar}C substrate bias temperatures, and lower laser scan velocities within the range of evaluated parameters. The incidence of microcracking in the laser scanned region also decreased with increasing substrate bias temperature. The thickest ({dollar}sim{dollar}200 {dollar}mu{dollar}m thick) deposit showed small microcracks by SEM that were not observed on less thick deposits.; Limited Raman spectroscopy and FTIR spectroscopy indicated that SALD from methane and hydrogen mixtures resulted in the formation of 3C-SiC when silicon wafer substrates were used. No Raman shifts were found that could be attributed to carbon. Transmission FTIR spectroscopy showed no characteristic absorption due to diamond or C-H stretching in the laser scanned regions. Auger depth profiling spectroscopy also indicated that carbon was not forming a film on top of the silicon, but rather it was diffusing into the substrate.; Random plasma instabilities caused capacitance manometer output fluctuations that caused a loss of control of chamber pressure. This problem was corrected by an active 5{dollar}sp{lcub}underline{lcub}rm th{rcub}{rcub}{dollar} order DC accurate low pass filter placed in line between the manometer and the pressure controller. This filter design can be readily employed to improve pressure control in plasma reactors used for etching, deposition, and polymerization.