EFFECT OF LOW TEMPERATURE PROCESSING ON POLYSILICON THIN FILM TRANSISTORS

POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS HAVE BEEN SUCCESSFULLY APPLIED TO LIQUID CRYSTAL DISPLAYS ON HARD (SOFTENING POINT ABOVE 600 DEGREES CENTIGRADE) GLASS SUBSTRATES, DEMONSTRATING THE ADEQUACY OF THEIR ELECTRICAL CHARACTERISTICS FOR SUCH APPLICATIONS. HARD GLASS SUBSTRATES WERE USED BECAUSE OF THE HIGH PROCESSING TEMPERATURES NEEDED FOR THE POLYSILICON TRANSISTORS. SIGNIFICANT COST SAVINGS COULD BE REALIZED, ESPECIALLY FOR LARGE DISPLAYS, IF A BOROSILICATE GLASS (CORNING 7059) COULD BE USED AS THE SUBSTRATE. HOWEVER, BOROSILICATE GLASSIS LIMITED TO 575 DEGREES CENTIGRADE PROCESSING TEMPERATURE. THIS RESTRICTION AFFECTS THE ELECTRICAL PROPERTIES OF THIN-FILM TRANSISTORS. WE HAVE DEVELOPED A LOW TEMPERATURE (550 DEGREES CENTIGRADE)PROCESS FOR FABRICATING POLYCRYSTAL SILICON TFT'S. IN ORDER TO COMMERCIALIZE IT FOR DISPLAY APPLICATIONS, WE NEED TO FURTHER INVESTIGATE EFFECTS FROM THE SUBSTRATE, PLASMA DOPING, AND CHANNEL ETCHING AS WELL AS SELECT THE BEST INSULATOR.