Application of blue laser direct-writing equipment for manufacturing of periodic and aperiodic nanostructure patterns

This study presents the novel development of low cost, highly efficient blue laser direct-writing equipment for using mask-less laser lithography to manufacture periodic and aperiodic nanostructure patterns. The system includes a long-stroke linear motor precision stage (X, Y), a piezoelectric nano-precision stage (Y, θz), a 3-DOF (degrees of freedom) laser interferometer measurement system, and a blue laser direct-writing optical system. The 3-DOF laser interferometer measurement system gives the control system feedback for displacement (X, Y, θz) of the equipment. The laser processing equipment consists of a blue laser direct-writing optical head, a field-programmable gate array (FPGA) alignment interface, and an optical head servo controller. The optical head operates at a wavelength of 405 nm. Processing the nanostructures on thermo-reaction inorganic resists with precise control of the laser intensity, taking advantage of the threshold effect to exceed the limitations of optical diffraction, and reduces the nanostructure hole size. The equipment can be used to fabricate various periodic nanostructure patterns, aperiodic nanostructure patterns, and two-dimensional patterns. The equipment positioning accuracy is within 50 nm at a speed of 50 mm/s, and the minimum critical dimension can be achieved about 100 nm or so.     

Nano-precision diamond cutting tools achieved by mechanical lapping versus thermo-mechanical lapping

A comparison of lapping qualities of nano-precision diamond cutting tools achieved by the mechanical lapping versus thermo-mechanical lapping is carried out in this work. The experimental results indicate that in mechanical lapping, the removal rate is in the nanometric level, as evidenced by the groove depth ranging from several to tens nanometers. And as a result, a satisfied cutting edge radius is sharpened, ranging from 35 nm to 50 nm. In thermo-mechanical lapping, the material removal takes place not only on the surface apexes but also on the valley bottoms of grooves inherited in the previous mechanical lapping. However, the rake face has a damage layer induced by the previous mechanical lapping, and then the removal rate on the bottoms is slightly lower than that on the apexes in the initial lapping stage, as demonstrated by the lessened groove depth. Meanwhile, the successive departing of carbon atoms from diamond crystal lattice one by one is always necessary for the thermo-mechanical lapping, and resultantly, its removal rate is at atomic scale. As expected, a more sharpened cutting edge radius of less than 10 nm can be achieved. Moreover, the mechanical lapping is capable of finishing a surface roughness of 0.8 nm in Ra, but about 2.0 nm of thermo-mechanical lapping. Such difference implies that the achieved cutting edge radius is independent of the finally finished surface roughness but mostly decided by the dominant removal mode of lapped surface layer, i.e. its corresponding removal rate.     

Nano-precision measurement of diamond tool edge radius for wafer fabrication

In this paper, a non-destructive nano-precision measurement method for diamond tool cutting edge radius is presented. The basis of the method is that the profile of a tool cutting edge can be copied by indenting the tool cutting edge into the surface of a selected material, and that the copy of the profile can be measured at nano-precision level using AFM. The selected material elastic error compensation coefficient has to be determined to cancel out the effect of elastic spring-back. Copper was selected as the indentation piece material due to its (1) high rigidity and high density, (2) large Young’s modulus and (3) low yield strength. The elastic error compensation coefficient for the copper material is determined through the indentation of a tungsten carbide tool edge on the copper surface. By comparing the actual tool edge radius measured using scanning electron microscope (SEM) on the sectional view of the tungsten carbide tool with the one measured from the copied profile of the tool edge on the copper surface, the coefficient is obtained. Three diamond tool edge radii were obtained using the proposed method. Analysis is given for the accuracy of the proposed method, showing that as far as the error elastic compensation coefficient is consistent with the copper material used, the only source of errors with the measurement will come from the device for measuring the indented profile on the surface.