Due to the recent trend toward the use of thinner underlayers in VLSI chips, more precise endpoint monitoring is needed for etching processes. An endpoint monitoring method has been developed, which uses scribe-line detection through direct observation of film thickness. This procedure determines the endpoint by detecting the reflection intensity from scribe-lines on a wafer surface during etching processes. The special feature of this system is to detect the intensity of reflected light with a continuous spectrum, which uses a tungsten-lamp for irradiation, and an ND filter and a CCD sensor for detection. For Poly-Si etching, the detection of reflected light with a continuous spectrum (wave length : 350 to 1050 nm) from Poly-Si is able to decide two points of residual thickness (600±50 Å, 200±50 Å), which are very close to the endpoint.