To print the 0.13μm logic device pattern, both KrF and ArF lithography can be used and we have two lithography processes for 0.13μm technology. In this paper, we evaluate whether ArF lithography process has enough process margin or not, when KrF HT-PSM is applied to ArF lithography processes. To estimate the feasibility of KrF HT-PSM in ArF lithography process, we simulated the change of the proximity effect according to illumination conditions and selected an optimum illumination condition. In that condition, we investigated the changes of ID bias, linearity and lineend shortening effect (LES) of minimum pattern. ID bias and CD linearity of isolated line in the ArF lithography matched well with those in KrF lithography on the optimized illumination condition. The differences of ID bias and linearity are less than 5nm. Line end CD difference between two processes is under 10nm. The ArF lithography process has enough process margins in optimized illumination condition with KrF Ht-PSM. Therefore, in the optimized illumination condition, KrF Ht-PSM can be applied to ArF lithography process to print pattern for the 0.13 μm logic device without mask revision.
As the IC industry is moving toward 90nm node or below, the critical dimension size of implant layers has shrunk to 250nm or smaller. To achieve better CD uniformity, dyed KrF resist and top anti-reflective coating (TARC) are commonly used in advanced photo process of implant layers, while typical organic BARC are not used because it requires dry etch process that damages the substrate and needs additional process steps. In order to overcome those shortcomings, developable BARC is introduced. It is a new type of BARC which is soluble to developer, TMAH solution, in the resist development step. This developer-soluble KrF BARC consists of polyamic acid and its solubility to alkaline could be adjusted by changing bake condition. In this experiment, we evaluated the margin of developable BARC process. Developable BARC reduces the standing wave of photoresist and improves the ID bias and CD uniformity as applied to implant feature printing. However, Developable BARC has a narrow thermal process margin. It is the profile of developable BARC that easily changes according to the coating thickness or thermal process conditions. Even in the same bake conditions, developable BARC profile changes according to the pattern densities. To observe the effects of developable BARC on the device performance, we compare electrical data of devices produced with and without developable BARC. They have the differences in the threshold voltage, leakage current and saturation current. Probably, the residues of the developable BARC after the development bring about the differences.
We have optimized the standard method for the extraction of MEEF at 200nm contact hole with regard to the pitch and mask CD variations, which resulted in 4.8. Additionally, we have evaluated the impact of mask bias, surrounding pattern size and asymmetric change of mask CD.
The pitch has greatly influenced the MEEF of the contact hole, and the contact holes with the minimum pitch show higher MEEF than isolated or semi-dense contact holes. The MEEF was little affected by the mask bias, ranging from 10 to 30nm. The MEEF remains independent despite the changes of the mask CD occurring around the holes within ±10nm range. The variations of the mask CD in one direction or another are not related to the MEEF determination. In addition, the pitch has influence on the defect printability. Other things that influence the defect printability are the defect types and their location. The defect of Cr intrusion has more intensive effect on the printed CD change. The more the defect is close to the center of the hole pattern, the more the defect printability increases.