[54] BROADBAND MICROSPECTROREFLECTOMETER
[75] Inventors: Adam E. Norton, Palo Alto; Chester L. Mailer}. Campbell; Hung V. Pham. San Jose; Paul Rasmussen, livermore, all of Calif.
[73] Assignee: KLA-Tencop. Corporation, San Jose, Calif.
[21] Appl. No.: 227,482
[22] Filed: Apr. 14,1994
Related U.S. Application Data
[63] Continuation of Ser. No. 899,666, Jun. 16,1992, abandoned.
[51] tot CL6 G01N 21/33
[52] U.S. Cl 250/372; 250/339.11; 356/448
[58] Field of Search 250/372,339.11;
356/448, 326, 328
[56] References Cited
U.S. PATENT DOCUMENTS
An improved method and apparatus for measuring the relative reflectance spectra of an observed sample (3) and method and apparatus for autofocussing the sample (3). A broadband visible and ultraviolet beam (42) is split into a sample beam (46) and a reference beam (48). The sample beam (46) is reflected off the surface of the sample (3), and the spectrum of the reflected sample beam (46) is compared to the spectrum of the reference beam (48) to determine the relative reflectance spectrum of the sample (3). A video camera (96) is provided for viewing the sample (3). The autofocus system has a course-focus mode and a fine-focus mode. In the course-focus mode, the sample (3) is focused when the centroid of the sample image is centered on a position sensitive detector (99). In the fine-focus mode, the sample is focused when the intensity of light reaching the detector (99) is minimized.
57 Claims, 7 Drawing Sheets
