High-resolution exposure equipment

As the physics and engineering of high-resolution exposure equipment advances with the advent of excimer-laser-powered, DUV projection printers... 

Nowadays, wafer steppers are used for the lithographic structuring of large diameter wafers at high resolution. This equipments use the step and repeat principle. Only small area of the substrate of about 1 cm is exposed to the mask in a single step. Afterwards, the substrate is moved to the next area followed by a subsequent exposure step and so on, which will be repeated until the entire wafer is exposed to the mask. 

Further, economic factors also constrain the utilization of microstructure fabrication technology. These are die factors diat control the cost of production, such as throughput, the rate at which substrates can be processed by the fabrication tools, capital investment required, and demands on operator time and skill. Electron beam exposure, for example, provides high resolution but uses expensive equipment that works slowly. Naturally, all of the elements of cost must be weighed against the value of (lie product produced. 

Lithography In order to precisely resolve the nanometer structures in microelectronics, various enhancement techniques have been applied to the current optical exposure tools that are equipped with deep UV light (193 nm wavelength). These enhancement techniques include phase-shift masks and immersion lenses (putting a liquid between final lens of the stepper and the wafer). The trade-off for the high resolution of modern steppers is an extremely small depth of focus (DOF) that is around 0.5pm over a typical field size of... 

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