The minimum feature size of the semiconductor device will be smaller and smaller because of the increasing demand for the high integration of the device. According to recently proposed roadmap, ArF immersion lithography will be used for 65 nm to 45 nm technology nodes. Polarization effect becomes a more important factor due to the increasing demand for high NA optical system and the use of immersion lithography. It is important to know that the polarization effect is induced by mask in small size patterning. The unpolarized plane waves leaving the illumination system are diffracted by the mask. So the light beam going through the mask will experience induced polarization by the mask. In this paper, we considered the change of polarization state as a function of mask properties. We calculated vector diffraction of 193 nm incident light. The masks considered are the chromeless mask, a binary chrome mask and 6 % attenuated phase shifting mask. We use the finite-difference time-domain method to solve the Maxwell equation. The aerial image depends on the polarization states induced by the mask properties such as materials, thickness, and pitch.
The desired minimum feature size is decreasing for the future technology nodes. Immersion lithography has been actively pursued as a method of extending the resolution of optical lithography beyond 65 nm mode. Immersion lithography and hyper NA impact the selection and optimization of the various resolution enhancement techniques (RET). These can be selected as appropriate for each mask pattern. As the line width on target is narrower, the fine-line structure will no longer be discernible. Then this is the resolution limit of the system. Until recent times, the traditional means of determining the quality of an optical element or system of elements was to evaluate its limit of resolution. A useful parameter in evaluating the performance of a system is the modulation transfer function and this is analyzed for the hyper NA immersion lithography.
Resolution enhancement technology (RET) refer to techniques that extend the usable resolution of an imaging system without decreasing the wavelength of light or increasing the numerical aperture (NA) of the imaging tool. Off-axis illumination (OAI) and phase shift mask (PSM) are essentially accompanied with optical proximity correction (OPC) for most devices nowadays. In general, these three techniques do not work in isolation and the most aggressive mainstream lithography approaches use combinations of all RETs. In fact, OAI and PSM are essentially useless for typical chip-manufacturing applications unless accompanied by OPC. For low k1 imaging, strong OAI such as Quasar or dipole illumination types is the best. We used dipole illumination in this study. By using strong OAI, the amplitude of the 0th order is decreased and the amplitude of the 1st order is increased. Chromeless phase lithography (CPL) is one of PSM technologies and CPL mask is the possible solution for small geometry with low mask error enhancement factor (MEEF). CPL uses only 180 degrees phase-shifter on transparent glass without chromium film to define light-shielding region, destructive interference between light transmitted through the 0 degree and 180 degrees regions produces dark images. To obtain the best resolution, proper OPC is required with CPL. While the most common and straightforward application of OPC is to simply move absorber edges on the mask by giving simple mask bias, the interesting and important additional technique is the use of scattering bars. Also, we can use zebra patterns for the transmission control. Mask intensity transmission changes can impact the image quality. Zebra patterns are formed by adding chromium transverse features. The transmission will be controlled by the zebra pattern density. Technology node with ArF source is studied and the mask optimization is found to be a critical. And the linewidth of scattering bars, transmission (using zebra feature) are varied at line and space (L/S) patterns. We used 65 nm node 5 L/S and 45 nm node isolated line pattern. In order to optimize the zebra pattern density, we need to control the line width and pitch of the zebra patterns. For dense line and isolated line, the use of scattering bars and zebra patterns affected target critical dimension. We found out the better process window at dense 65 nm node by comparing the use of scattering bars with zebra patterns. Likewise, we optimized the isolated 45 nm node.