Multi-generation device fabrication by ArF lithography

Abstract

Although ArF excimer laser lithography is expected to attain the highest resolution possible in optical lithography, its application to 0.13-pm devices has not yet adequately demonstrated. In next generation sub-0.10 pm devices, it is believed that the mix and match process is indispensable with optical lithography and other types of lithography. One of the reason is the difficulty of fabricating contact holes with a larger process margin. Here, we demonstrate that it is possible to make 0.13-pm patterns using a single layer resist in combination with resolution enhancement techniques, and to make sub-0.10 ym contact holes using the Top Surface Imaging (TSI) process. Figure 1 shows a pattern formed by using a single layer resist of the alicyclic group. The process for this high resolution resist is based on an analysis of methacrylate copolymer by percolation theory. Figure 2 shows the diffusion contrasts calculated by simulation and experiment results of dissolution rate measurement for methacrylate copolymer. This resist has excellent performance through the use of an alternating phase shifting mask (PSM), as shown in Fig. 3. We observed that bottom anti-reflective coating (BARC), and annular illumination could extend the depth of focus (Table 1, Table 2). Using such techniques, we obtained 0.12-pm resist patterns of actual devices (Fig. 4).We have already reported that the TSI process can be used to fabricate a sub-0.10 pm L&S.We tried to make contact holes using NTS-4 (Sumitomo Chemical Co., Ltd.). Silylation was done by dimethylsilyldunethylamine (DMSDMA) in the vapor phase. Then, silylated resist was developed in 02-SO2 plasma. The exposure tool was an IS1 stepper (1OX reduction and 0.6-NA).A good pattern profile for a 0.09-pm contact hole was obtained ( Fig. 5(a)). A high sensitivity of 20 mJ/cm2 was also achieved. This process was optimized by theoretical calculation methods.We etched 1.0-pm thickness Si02 film using this resist pattern as a mask. A vertical contact hole pattern (aspect ratio 12) was obtained, as shown in Fig. 5 (b). After dry etching, the resist was successfully removed by 0 2 ashing without residue, as shown in Fig. 5 (c). We evaluated the process margin for this procedure. A exposure latitude of +/-lo% was obtained with a 0.10-pm contact hole (Fig. 6). A focus latitude of 0.3 pm was obtained for the Cr mask (Fig. 7).We obtained a 0.5-pm DOF using an attenuated phase shifting mask. This indicate that this process is suitable for dynamic planarization substrates such as those in the CMP process.We demonstrated that ArF lithography is able to be applied to multi-generation device fabrication of 0.13-ym process using a single layer resist and a sub-0.10 pm process using TSI.

Theoretical and Experimental Study on the Silylation of Alcohol Units in ArF Lithography Resists.

“…24 The silylation process is thus a promising TSI process for use when the design rule is below 0.10 µm.…”