The increasing speed of technology innovation has demanded faster computer chips and forced integrated circuit (IC) manufacturers to create smaller feature sizes on chips to meet this demand. The semiconductor roadmap has slated feature sizes to be reduced to 90nm in 2004 with continuing to decreases in the following years. Until recently, ion implant layers were not considered critical layers, and many fabricators still use 365nm exposure with dyed resists on these layers. However as implant feature sizes decrease to 250nm or smaller and overlay restrictions are tighter, KrF exposure is required for the ion implant photolithography process. Currently dyed KrF resists are limited in their resolution and their ability to control critical dimensions (CD) due to reflectivity of the substrates. A bottom anti-reflective coating (BARC) is desirable to help control substrate reflectivity and improve CD control. Until now the only solutions for using a BARC under KrF resist are inorganic and organic thermoset BARCs. These two solutions require plasma etch to remove them before the implant process. Plasma etch is undesirable in the implant process for two reasons; the first is damage to the underlying substrate and the second is increased cost of processing time to perform the BARC plasma etch. With a developer soluble BARC, the BARC is removed during the development of the photoresist, resulting in a minimal effect on wafer throughput as well as no permanent effects to the underlying substrate. In this paper we will discuss the chemistry behind a novel developer soluble BARC as well as the processing conditions used for testing these materials. We will also show results using these materials with various photoresists.
Dual Damascene (DD) process has been implemented in manufacturing semiconductor devices with smaller feature sizes (<EQ 0.20 micrometer), due to increased use of copper as a metal of choice for interconnects. Copper is preferred over aluminum due to its lower resistance which helps to minimize the effects of interconnect delays. Via first DD process is the most commonly used process for manufacturing semiconductor devices since it requires less number of processing steps and also it can make use of a via fill material to minimize the resist thickness variations in the trench patterning photolithography step. Absence of via fill material results in non-uniform fill of vias (in isolated and dense via regions) thus leading to non-uniform focus and dose for exposure of the resist in the deep vias. This results in poor resolution and poor critical dimension (CD) control in the trench-patterning step. When a via fill organic material such as a bottom anti- reflective coating (BARC) is used, then the resist thickness variations are minimized thus enhancing the resolution and CD control in trench patterning. Via fill organic BARC materials can also act as etch blocks at the base of the via to protect the substrate from over etch. In this paper we review the important role of via fill organic BARCs in improving the efficiency of via first DD process now being implemented in semiconductor manufacturing.
A fast-etching broad band bottom anti-reflective coating (BARC) for photoresist applications at the wavelength of 365nm, 248nm and 193nm was developed. The new BARC formulated in safe solvents such as ethyl lactate and PGME exhibits wide spin bowl compatibility with various photoresists, and can be processed with common edge bead removal solvents. The optical properties of the new BARC are tailored for high contrast resist systems, with film optical density exceeding 4.2 micrometers at 365 nm, 7.5 micrometers at 248 nm and 8.5 micrometers at 193 nm. Most importantly, we have demonstrated plasma etch rates of the new coating in excess of 1.5-2.0 times that of conventional i-line and DUV photoresist. The compatibility of this material with multi resists at all three wavelengths will be discussed as well as trade-offs versus dedicated single wavelength BARC systems.