Hiroshi Nagaike

Particle reduction and control in plasma etching equipment

Particles within plasma etching equipment stick to the wafer and cause defects, resulting in large scale integrated circuit (LSI) yield reduction. We observed the behavior of particles resuspended in a vacuum chamber using a laser light scattering method. Investigating the influences of gases, static electricity, and plasma on particle resuspension, we found out that particles are not only suspended by the shock wave or gas viscous force generated when the valve opens or when the gas is introduced into the chamber, but also are resuspended due to electromagnetic stress caused by electrostatic chuck voltage application or radio frequency discharge. If, on the other hand, stable plasma generation is assured, particles are positively charged and receive repelling force within the ion sheath; as a consequence, particle resuspension is suppressed. We developed a method that can suppress particle resuspension by avoiding the production of a shock wave and electromagnetic stress during the wafer processes. We also developed a method that can effectively remove particles before the beginning of processes that use gas viscosity, the shock wave, and the electromagnetic stress.

Observation and evaluation of flaked particle behavior in magnetically enhanced reactive ion etching equipment using a dipole ring magnet

An in situ particle monitoring system using laser light scattering method was installed onto a commercially available radio frequency (rf) plasma oxide-etching tool that is enhanced magnetically using a dipole ring magnet. We observed the behavior of particles that flaked off the deposition film. It can be proven that the flaked particles have different trajectories depending on the magnetic field. When no magnetic field is applied, the flaked particles make a reciprocating motion near the grounded electrode due to the positive charge of flaked particles within the sheath. Alternatively, flaked particles enter the bulk plasma in response to a small gradient of electrical potential near the upper electrode when the magnetic field is active. Particles typically move horizontally with vertical vibration in bulk plasma using a magnetic field. The main force acting on the particles is electrostatic in nature.

In Situ Particle Monitors: The Next Level of Yield Control for Critical Processes

In situ particle monitors (ISPM) have been used in the semiconductor industry for many years to monitor chamber condition before and after preventative maintenance. New improvements in particle detection technology combined with novel methods to remove particles from the chamber are proving that ISPM technology is a key component in the fight to improve product yields.

Study of ADI (After Develop Inspection) on photo resist wafers using electron beam (II)

We have clarified that the low-damage, high-resolution defect inspection of the photo resist patterns is ensured by the electron-beam defect inspection equipment for 32-nm generation and beyond. It has first been confirmed that the CD variations on the 65-nm width line structure formed on an ArF resist under general inspection conditions are equal to or less than the CD variations due to a general CD-SEM. We have also succeeded in understanding the resist deterioration mechanism when the ArF resist is exposed to e-beams. This understanding has led us to learn that the layer that, located in the vicinity of the resist surface, is deteriorated by e-beams has its etching rate lowered to cause even improvement on the etching resistance. These findings have enabled us to use inspection conditions that cause lower damage to resists. By using those conditions, we have been able to inspect ArF resist line-space structure wafers with line width of 65nm and pitch width of 140nm. The inspection successfully detected 15 to 20nm programmed extrusion defects with a capture rate of at least 95% and a nuisance rate of 5% or less. It has thus been revealed that e-beam defect inspection equipment are useful for inspecting defects on resist wafers with 32-nm generation and beyond.

Nano-thickness Stellar Defects

New type defects which are nanometer-thickness stellar shape defects called as the stellar defects are reported. Since the stellar defects need the center particle and the water to form, we successfully have reduced the stellar defects by reducing the particles and humidity in the chamber. These very thin defects must be key issues in the processes that we have to control nanometer thickness.