Toshiei Kurosaki

0.3-micron Optical Lithography Using A Phase-Shifting Mask

Improved resolution of an available i-line (365nm) stepper using a phase-shifting mask is discussed. The resolution investigated here is not only for periodic lines but also for isolated spaces and hole patterns. To obtain a narrow bright line for printing a fine isolated space on a wafer, two additional line apertures with widths smaller than the critical dimension of the stepper lens are placed on each side of the main aperture of the mask. The optical phase of the main aperture and those of additional apertures are opposite. The additional apertures play a role in reducing the bright feature size to less than the line spread function of the lens. Similarly, printing a fine hole is accomplished by using a main aperture surrounded by four additional apertures. The intensity distribution on the wafer is calculated by comparing the results obtained with a phase-shifting mask and those obtained with a conventional transmission mask. Patterns are also printed on the wafer using an i-line stepper with a nominal 0.55 μm resolution. A pattern of 0.3-μm lines and spaces, 0.3-μm isolated spaces and 0.4-μm hole patterns are resolved using the phase-shifting mask. This resolution is impossible with a conventional transmission mask. The effects of variations in the optical phase of the additional apertures are also investigated. The intensity calculations and experimental results suggest that it is possible to control the position of the best focal plane by changing the optical phases of the additional apertures.

Improved resolution of an i‐line stepper using a phase‐shifting mask

Improved resolution of an available i‐line (365 nm) stepper using a phase‐shifting mask is discussed. The resolution investigated here is not only for periodic lines but also for isolated spaces and hole patterns. To reduce the sizes of isolated space images for printing fine single spaces on a wafer, two additional line apertures with widths smaller than the critical dimension of the stepper lens are placed on each side of the main aperture of the mask. The optical phase of light passing through the main aperture and those through additional apertures are opposite. The additional apertures play a role in reducing the bright feature size to less than the line spread function of the lens. Similarly, printing a fine hole is accomplished by using a main aperture surrounded by four additional apertures. The intensity distribution on the wafer surface is simulated by comparing the images obtained with a phase‐shifting mask and those obtained with a conventional transmission mask. Printing fine patterns are per...

Chip leveling and focusing with laser interferometry

A new chip leveling and focusing method has been developed which uses interferometry with a laser beam which has S-polarization and a large incident angle to the exposure surface of an LSI wafer and thereby leveling and focusing accuracy is maintained regardless of the kinds of layers on the wafer. A pilot model of this type of detection method demonstrated a leveling and focusing accuracy of about and 1.

New 5X i-Line Projection Aligner For VLSI Fabrication

A new i-line projection aligner, the LD-5010i, has been developed and has two primary features : good patterning ability and good overlay accuracy. In this paper, performance of the i-line projection system and the characteristic alignment method, called the two-wavelength detection, are described.

Contrast improvement of alignment signals from resist coated patterns

A method of enhancing the contrast of alignment signals for use in step‐and‐repeat projection aligners is described. In conventional through‐the‐lens alignment, signals are greatly influenced by interference phenomena between the resist surface and the wafer surface. Factors such as resist thickness, step depth, and alignment wavelength are examined to determine their effect on signal contrast. Based on the results, two wavelengths (i line/e line) are used for alignment and an alignment accuracy of 0.13 μm is obtained.

Position sensing of a grating mark by heterodyne detection using a Zeeman laser

A way to detect with high resolution the position of a wafer and a mask is proposed and evaluated. In this method, a grating mark on a wafer or a mask is detected by heterodyne interference using a He-Ne Zeeman laser. Experiments show that the position of a wafer or a mask could be detected with a resolution of approximately 0.01 microm.

Development of noncontact positioning apparatus with large outlet pneumatic gauge for reduction projection aligner.

Reduction projection aligner needs a noncontact measurement means for the position of the wafer surface. A pneumatic gauge is suitable to detect the position of the wafer surface coated with several materials. The pneumatic gauge for this purpose has large outlet diameter which equals the reduction projection area. It must work under large operation gap and at the same time extremely low flow rate for semiconductor process. In this paper, design method and accuracy of the noncontact positioning apparatus with the large-outlet pneumatic gauge and some experimental results are described. Main results obtained are as follows: (1) Positioning accuracy depends mainly on pressure transducer accuracy. (2) Developed apparatus having a 20 mm outlet diameter, and a 90 μm gap, has achieved a positioning acuracy of 0.08 μm (3σ) under low flow rate (0.4l/min).