Tomohiro Goto

Film stacking architecture for immersion lithography process

In immersion lithography process, film stacking architecture will be necessary due to film peeling. However, the architecture will restrict lithographic area within a wafer due to top side EBR accuracy In this paper, we report an effective film stacking architecture that also allows maximum lithographic area. This study used a new bevel rinse system on RF3 for all materials to make suitable film stacking on the top side bevel. This evaluation showed that the new bevel rinse system allows the maximum lithographic area and a clean wafer edge. Patterning defects were improved with suitable film stacking.

Analysis of the Effect of Mechanical Strength of the Resist Film on Pattern Collapse Behavior Using Atomic Force Microscope

Recently, pattern collapse is becoming one of the critical issues in semiconductor manufacturing and many works have been done to solve this issue1) 2). Since pattern collapse occurs when outer force onto the resist pattern such as surface tension, impact of rinse solution, etc. surpasses the resistance of the resist pattern such as mechanical strength, adhesion force between resist and substrate, it is considered effective for improvement of pattern collapse to control resist film properties by track process, i.e., optimization of the mechanical properties of the resist film and enhancement of the adhesion force between resist and substrate3) -5). In this study, we focused on the mechanical strength of the resist film and examined how post applied bake (PAB) condition affects the pattern collapse behavior. From ellipsometry measurement, it was found that increasing PAB time and temperature resulted in thickness reduction and refractive index increase, which suggested that the density of the resist film became high. Then we analyzed the mechanical strength of the resist film with the tip indentation method using atomic force microscope. It was found that the hardness of the resist film was affected by PAB conditions and regardless of PAB condition, hardened layer existed beneath the film surface. Finally, we carried out the measurements of loads to collapse 180nm resist dot patterns using the direct peeling with atomic force microscope tip (DPAT) method. Loads ranged from 600 to 2000nN overall and essentially increased as seen for indentation measurements when PAB temperature or time was increased, except some critical conditions. Through these evaluations using AFM, we succeeded in quantitatively evaluate the mechanical properties of the resist films processed with various PAB conditions. It was found that PAB condition obviously impacts on the hardness of the resist film and it is closely related to pattern collapse load.

Backside EBR process performance with various wafer properties

In immersion lithography process, film stacking architecture will be necessary to avoid top coat film peeling. To achieve suitable stacking architecture for immersion lithography process, an EBR process that delivers tightly controlled film edge position and good uniformity around the wafer circumference is needed. We demonstrated a new bevel rinse system on a SOKUDO RF3 coat-and-develop track for immersion lithography. The performance of the new bevel rinse system for various wafer properties was evaluated. It was found that the bevel rinse system has a good controllability of film edge position and good uniformity around the wafer circumference. The results indicate that the bevel rinse system has a large margin for wafer centering accuracy, back side particles, wafer shape and substrates with good film edge position controllability, uniformity and clean apex. The system has been demonstrated to provide a suitable film stacking architecture for immersion lithography mass production process.