cleaning procedures than you would for CD or CD-ROM manufacturing. Spinning of the photoresist also has a greater challenge associated with it. There are some defects that are tolerable in CD and CD-ROM manufacturing that are not tolerable for CD-R masters. Special attention must be given to the processes, to minimize “voids” and “PR Gels” that are frequently present in thin film applications. Some of the CD-R master manufacturers place special requirements on the phot-oresist thickness and uniformity. The photoresist thickness is critical to the success of the coating process. This is most often measured using an elipsometer. Thickness tolerances can be several orders of magnitude tighter than CD-ROM production. This requires careful monitoring during spinning and dispensing of the photoresist.
Mastering
   In mastering the preformatted grove is exposed. This groove is very critical for tracking while in the CD-R recorder. Careful control must be present when producing tightly specified grooved widths, depths, and wall angles. The grooved form used for CD-R mastering is referred to as ATIP (actual time is pre-groove). The groove is wobbled in a sinusoidal fashion which is formed by frequency modulating a carrier frequency of 22.05 kHz, one half the CD sampling frequency rate. The carrier contains motor control information used for servo purposes by the CD-R recorder. The time code information required by the CD-R recorder is derived from the modulation of the carrier frequency. The optical path is designed to efficiently modulate the laser at relatively high speeds to create pits for CDROM.  When 

mastering instead of modulating the acoustical carrier frequency inside the acoustical optical AO, the carrier is frequency modulated producing a variable grating for the recording laser. As the frequency changes, the spaces in the grating vary in width producing changes in the angle of deflection for the defracted laser beam. (The ATIP formatter for the wobble carrier, +I kHz.) By frequency modulating the AO carrier in conjunction with an optical beam expander, a sinusoidal deflection is formed with the recording beam producing the wobbled groove. The wobble amplitude on the resist master is typically 60 lim, peak-to-peak with a spatial period of 54 to 64 um. All the frequency modulations are produced by using an ATIP formatter instead of EFM formatter which is used for CD-ROM mastering.
   By differentiating the wobble from the radial error signal, the CD-R recorder receives all the necessary information for recording. The 22.05kHz carrier from the wobble is used for phase locking the recorder to the standard rotational speeds of 1.2 to 1.4 m/s. The FM signal contains time information, identical to the time encoding in subcode Q and in the CD-ROM headers. The ATIP is encoded in Binary Coded Decimal with the significant bit first. Time code is represented in minutes, seconds and frames (00:00:00) with 75 frames per second. In addition to normal time code, the wobble signal also contains information about recording zones, optimum recording powers, disc application codes and an error detection method using 14 bit CRC on minutes, seconds and frames. The wavelength used in the recorder can range from 775 to 800 nm. The optimurn recording