Development Process Control And Optimization Utilizing An End Point Monitor

Abstract

Photoresist linewidths are affected by many factors such as resist film thickness, solvent content, exposure dose, etc. As design rules shrink below 1 pm, quick and accurate determination of linewidths not only becomes more critical, it becomes more difficult. Fiber optic based reflectivity measurements during spray or spray /puddle development provide a process sensitive method of wafer inspection which may be used to optimize equipment and process setup. Critical dimension uniformity can be optimized by studying the uniformity of development in the inspection area. The correlation between changes in an end point uniformity measurement and the fmal linewidth is shown as a function of exposure dose variation, development spin speed, and developer dispense rate. A methodology is presented for determining optimum developer usage and equipment setup for a spray process.Reflectivity measurements provide a diagnostic capability as it provides a window into the resist film's dissolution profile. A study of the differences between development signals can reveal such processing problems such as resist lifting, scumming, and overbaking. Examples of several of these cases are given.

On‐line state and parameter Identification of positive photoresist development

“…The resulting signal, sinusoidal in nature, indicates the constructive and destructive interferences caused by the two reflections, thus allowing calculation of both the rate of development and the resist thickness of the developing region. Sautter et al (1989) expanded the work of Lauchlan et al to use the end point detector to monitor line width variation, development uniformity, and certain process failures. Mack (1983Mack ( , 1985 has presented a mathematical model which describes the development process.…”