| The semiconductor development drive the production design rules more and more small. In 300 mm fabs, current production ground rules are from 90 to 45 run while in 200 mm fabs, the production rules are from 180 nm to 110 run. The lithography technology is the drive force for the IC development all the time. It is the center of the semiconductor manufacture process, it is also the most costly, complicated and pivotal process. The lithography process cost will become higher for wafer manufacturers when they use shorter exposure wavelength. It is more than 30 percent in the total manufacture cost, the percentage will be increase in the 90nm, 65nm node process, especially when the technology developing to 32nm and more small node design rules. For most manufactory, it is the most import that using the current resource to develop new technology process and manufacture in order to reduce the cost and gain maximal proceeds. This thesis will show our research about 90nm technology node process with KrF photo resists. It would help 200mm foundry companies use KrF scanner to develop sub-0.11um technology node process. At the same time, it is also an interesting topic for 300mm foundry companies to transfer ArF process to KrF process to reduce process cost with acceptable lithography performance.Due to that the KrF photo resists are originally designed for ground rules greater than 110 nm, such as, 130 nm structures, it is relatively unknown how feasible it is to extend their performance to below 110 nm. So this thesis will explore the photo resists performance under 90 run design rules firstly. The factors of affect the photo resist characteristic including develop capability, reaction threshold energy, acid diffusion and so on. The acid diffusion is the main characteristic of KrF photo resists CD uniformity, so we mainly explore the acid diffusion in this thesis. The diffusion of photo acid, which is necessary for the catalyzed cross linking or de-linking molecular reactions, can degrade aerial image due to its random nature. For random diffusion of photoacid, the Diffusion function is a Gaussian convolution. We will show our study on effect of the variation of acid diffusion length to the process window among 3 production KrF photo resists.To support continuing design rule shrink semiconductor chips, more and more efforts have been invested in the understanding of optical proximity effect (OPE). In OPE, the most difficult structures are those extending in both X and Y directions, or 2-dimensional (2D) patterns, such as, line end shortening, corner rounding, etc. This thesis will also explore the KrF photo resists line end shortening (LES) performance under 90 nm design rules and will explore the performance dependence on imaging conditions.We have found that the effective photo resist acid diffusion length is not constant for different photo resists and is also not constant for a certain photo resist under different line and space combinations. For the photo resists LES, At 100 nm CD, before OPC, the LES per edge is < 100 nm, at 120 nm CD, the LES per edge is < 75 nm, which is found to be stable and acceptable for 90 nm process. Both PEB and NA settings can affect LES significantly, PEB has bigger effect in isolated line ends while NA setting seems to affect dense line ends more.For the 90 nm design rules technology process with the KrF photo resists, we will show our study result for critical layers - Gate poly, Metal1 and Contact. The process window, CD through pitch and MEEF are checked. The result show KrF process with high NA exposure tool is acceptable to meet the 90nm technology node requirement. |
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