摘要 |
WHEN THE SECOND HARMONIC OF A YAG LASER IS IRRADIATED ONTO SEMICONDUCTOR FILMS (302), CONCENTRIC-CIRCLE PATTERNS ARE OBSERVED ON SOME OF THE SEMICONDUCTOR FILMS (302). THIS PHENOMENON IS DUE TO THE NON-UNIFORMITY OF THE PROPERTIES OF THE SEMICONDUCTOR FILMS (302). IF SUCH SEMICONDUCTOR FILMS (302) ARE USED TO FABRICATE TFTS, THE ELECTRICAL CHARACTERISTICS OF THE TFTS WILL BE ADVERSELY INFLUENCED. A CONCENTRIC-CIRCLE PATTERN IS FORMED BY THE INTERFERENCE BETWEEN A REFLECTED BEAM 1 REFLECTED AT A SURFACE OF A SEMICONDUCTOR FILM (302) AND A REFLECTED BEAM 2 REFLECTED AT THE BACK SURFACE OR A SUBSTRATE (300). IF THE REFLECTED BEAM 1 AND THE REFLECTED BEAM 2 DO NOT OVERLAP EACH OTHER, SUCH INTERFERENCE DOES NOT OCCUR. FOR THIS REASON, A LASER BEAM IS OBLIQUELY IRRADIATED ONTO THE SEMICONDUCTOR FILM (302) TO SOLVE THE INTERFERENCE. THE PROPERTIES OF A CRYSTALLINE SILICON FILM FORMED BY THIS METHOD ARE UNIFORM, AND TFTS WHICH ARE FABRICATED BY USING SUCH CRYSTALLINE SILICON FILM HAVE GOOD ELECTRICAL CHARACTERISTICS.FIG.1 |