Yukio Kenbo

X-Ray Exposure System With Plasma Source For Microlithography

An x-ray exposure system with a plasma source has been developed to be applied in R & D of a deep-submicron device fabrication process. This system features high accuracy align-ment using imaging optics with high-speed signal processing, precision proximity gap control by means of a wafer surface flattening mechanism, and fine pattern replication by incorporating a plasma focus soft x-ray source. The imaging optics are arranged to be diagonally symmetric with respect to the x-ray exposure axis to perform continuous pattern detection (lateral displacement and gap) directly in an exposure field. A unique wafer chuck capable of flattening a wafer surface to within ±0.5 μm by piezoelectric actuators, supported by a six-axis, micro-motion mechanism, makes it possible to align the wafer to the mask (resolution of 0.01 μm) with a uniform gap (15=11 μm). The plasma focus source which emits x-rays with wavelengths in the range of 10 ~ 14 Å from high-temperature neon plasma using the pinch effect induced by a pulse current, has been newly developed. The pattern replication performance is thoroughly examined, showing an alignment accuracy of within ±0.1 μm (2σ), and a fine pattern replication of 0.3 μm.

Using high frequency acoustic micro imaging to detect defects in artificial micro void specimens

We have studied the acoustic characteristics of echoes reflected from micro void areas. Artificial-defect samples with air gap widths of 30, 50, and 70 μm were developed. Echo signals from the samples were obtained in a pulse-echo experiment with a high-frequency ultrasonic probe (center frequency: 200 MHz). Wave propagation for an artificial-defect model was also simulated by using a finite element method. Calculation and experimental results confirmed that phase shifts and ringing are useful for distinguishing between normal and defective samples. Simulation results show that defect detection is possible for gap widths of less than 10 μm.

Development of a particle-detection system for phase-shifting masks

Particles as small as 0.34 micrometers are detected on phase-shifting masks for 0.3 micrometer LSIs by the particle detection system PS-6000. The system detects the forward- scattered light from the particles using illumination through the rear surface of the masks.