Application and Improvement of CU CMP Thickness Control Method Based on R2R System

In the back-end-of-line (BEOL) chemical mechanical polishing (CMP) process, the copper wire barrier material (Ta/TaN) and the underlying low dielectric (Low-K) material exhibit limited optical, physical, or chemical properties, which results in low-contrast signal. Consequently, reliable endpoint detection for barrier polishing poses significant challenges, leading to the common practice of employing fixed-time polishing. Due to non-ideal factors such as machine conditions and the lifespan of consumables, the amount of polishing is frequently either excessive or insufficient, leading to product film thickness that exceeds specifications and negatively impacting yield. This paper introduces a self-feedback run-to-run (R2R) system designed to automatically control polishing time on a wafer-to-wafer manner, facilitating the automatic regulation of copper wire thickness, stabilizing resistance, and enhancing product yield. Furthermore, an optimization method for the R2R system algorithm is proposed to improve feedback response time and minimize errors in copper thickness control.