METHOD AND APPARATUS FOR ENDPOINT DETECTION FOR CHEMICAL MECHANICAL POLISHING

An apparatus to generate an endpoint signal to control the polishing of thin films on a semiconductor wafer surface includes a through-hole (112) in a polish pad (109), a light source (117), a fiber optic cable (122), a light sensor (115), and a computer (121). A pad assembly includes the polish pad (109), a pad backer (120), and a pad backing plate (140). The pad backer (120) includes a pinhole (111) and a canal that holds the fiber optic cable (122). The pad backer (120) holds the polish pad (109) so that the through-hole (112) is coincident with the pinhole opening (111). A wafer chuck (101) holds a semiconductor wafer (103) so that the surface to be polished is against the polish pad (109). The light source (117) provides light within a predetermined bandwidth. The fiber optic cable (122) propagates the light through the through-hole opening (112) to illuminate the surface as the pad assembly orbits and the chuck (101) rotates. The light sensor (115) receives reflected light from the surface through the fiber optic cable (122) and generates reflected spectral data. The computer (121) receives the reflected spectral data and calculates an endpoint signal (125). For metal film polishing, the endpoint signal (125) is based upon the intensities of two individual wavelength bands. For dielectric film polishing, the endpoint signal (125) is based upon fitting of the reflected spectrum to an optical reflectance model to determine remaining film thickness. The computer (121) compares the endpoint signal (125) to predetermined criteria and stops the polishing process when the endpoint signal (125) meets the predetermined criteria. L'invention porte sur un appareil produisant un signal de point d'extrémité (125) de commande du polissage de films minces déposés à la surface de tranches de semi-conducteurs comportant un trou traversant (112) pratiqué dans un patin (109) à polir, une source lumineuse (117), un câble (122) à fibres optiques, un détecteur (115) de lumière, et un ordinateur (121). Le patin (109) comprend un tampon (109), un renfort (120) et une plaque (140) support. Le renfort comporte un trou d'épingle (111) et un canal pour le câble (122) de fibre optique. Le renfort (120) est placé de manière à ce que le trou traversant (112) coïncide avec le trou d'épingle (111). Un mandrin (101) maintient la tranche de semi-conducteur pour que la surface à polir porte sur le tampon (109). La source lumineuse (117) fournit une lumière d'une largeur de bande prédét