It is well known in the industry that hot acid processes, such as the use of phosphoric acid to etch nitride or sulphuric acid and hydrogen peroxide to strip photoresist, add thousands of particles to the wafer surface (Figure 1). It is therefore common practice to follow these processes with a cleaning process to remove the particles. The cleaning process typically involves treatment with SC1 (H₂O + NH₄OH +H₂O₃) followed by megasonic treatments. The SC1 solution slightly undercuts the particles, presumably reducing their adhesion to the surface. The megasonic treatment then dislodges the particles with ultrasonic energy generated by the implosion of microscopic gas bubbles. As feature sizes continue to decrease, the side effects of the SC1/megasonic cleaning processes have become significant. In particular, the additional etching of one to two angstroms of material by the SC1 solution and the potential for megasonic damage to delicate device structures become problematic. The new process, developed by FSI for its MAGELLAN^® Immersion Cleaning System, eliminates the etching associated with SC1 and the damage caused by megasonic treatment.

Figure 1: Hot acid processes, such a nitride etching with phosphoric acid and resist stripping with sulphuric acid, are notoriously dirty. When followed only by rinsing with DI water they typically add thousands of particles (left). FSI’s new cleaning process removes the particles (right) without the additional etching or damage associated with SC1/megasonic cleaning processes.

The MAGELLAN^® System is a 200/300mm immersion cleaning system designed to meet the challenges of advanced IC development and manufacturing through its unparalleled process performance and configurability. Its innovative design includes multiple proprietary technologies. FSI’s exclusive STG^® (surface tension gradient) rinse and dry technology speeds cycle times. APC (advanced process control), SymFlow^® HF etch and MegaLens™ acoustic diffuser work together to guarantee high process consistency, etch uniformity and particle removal efficiency. The system supports a wide range of chemistries from concentrated to dilute with advanced chemical delivery, active closed-loop control and redundant monitoring. It can be configured with a single or multiple process modules to adapt precisely to customer process requirements. Wafer handling can be initially configured with a single robot for process development and characterization (250 wph), and later field-upgraded to the dual robot configuration to meet the demands of high-volume production (up to 400 wph). The MAGELLAN^® system leverages more than 30 years of FSI wafer cleaning experience to provide increased productivity, higher yields and greater flexibility across a broad range of cleaning applications.

Figure 2: Graphic comparison of particles added by hot acid process after three cleaning procedures: left - DI rinse only, middle – FSI’s proprietary cleaning process, right – industry standard SC1/megasonics

Table 1: Data supporting Figure 1

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