A frequent problem encountered by photoresists during the manufacturing of semiconductor device is that activating radiation is reflected back into the photoresist by the substrate. So, it is necessary that the light reflection is reduced from the substrate. One approach to reduce the light reflection is the use of bottom anti-reflective coating (BARC) applied to the substrate beneath the photoresist layer. The BARC technology has been utilized for a few years to minimize the reflectivity. As the chip size is reduced to sub 0.13-micron, the photoresist thickness has to decrease with the aspect ratio being less than 3.0. Therefore, new Organic BARC is strongly required which has the minimum reflectivity with thinner BARC thickness and higher etch selectivity towards resist. SAMSUNG Electronics has developed the advanced Organic BARC with Nissan Chemical Industries, Ltd. and Brewer Science, Inc. for achieving the above purpose. As a result, the suitable high performance SNAC2002 series KrF Organic BARCs were developed. Using CF4 gas as etchant, the plasma etch rate of SNAC2002 series is about 1.4 times higher than that of conventional KrF resists and 1.25 times higher than the existing product. The SNAC2002 series can minimize the substrate reflectivity at below 40nm BARC thickness, shows excellent litho performance and coating properties.
To reach the sub-0.3 micrometer contact hole pattern by i-line lithography, some advanced technology was introduced such as Phase Shift Mask (PSM) and/or photoresist (PR) flow process. It may be possible that the contact hole is patterned with 0.18 micrometer resolution by the PR flow process with PSM. However, PSM cause the Tg temperature of resist down at the phase shift area. And it also leads the bulk effect by the different pattern density at the cell edge. Thus, during the PSM + PR flow process, 'contact shift' and 'contact distortion' (so-called 'Eyebrow') defects are unavoidable. To repel these defects, we designed the new lithographic process; the UV-bake before thermal flow process. By the UV light at 130 +/- 10 degrees Celsius, the resist was cured at the resist surface. This surface-cured resist has the higher Tg temperature even the normal PSM reticle induces the Tg down. Top surface curing (hardening) also minimized the bulk effect. To maximize the UV bake effects, we developed new resist which was optimized to UV-bake process. By UV-bake process with new resist, the 0.2 micrometer contact hole was patterned. ET margin was 14 nm/10 mJ, and DOF margin was 0.6 micrometer at the mass fabrication device. The 'Eyebrow' and contact shift defects are not detected.