As linewidths continue to decrease in size, preventing smaller defects is becoming critical to maintaining yield. Defects that are caused during the development cycle and attach themselves to the BARC surface, such as water spots or photoresist residues, have always been a concern and have been usually removed at the expense of throughput. Various options are available to reduce these types of defects but each has disadvantages. One such example is a double puddle develop process. The disadvantage of this process is that the exposure dose may have to be changed. Another example is increasing the rinse time to several minutes with an associated reduction in throughput. This paper will discuss rinse alternatives that have been able to reduce develop type defects by up to 70% while also reducing the wafer-to-wafer variation by up to 80%. This process may have a dramatic increase in throughput by keeping the total rinse time under 20 seconds and may have minimal (less than 2% change) impact on measured linewidth. These rinse processes utilize a quick succession of changing spin speeds and accelerations that are acceptable for 300-mm wafer processing. Surfactant-containing rinse solutions designed to reduce line collapse in 193-nm photoresists were also investigated to determine their effectiveness in reducing post-develop defects in concert with the newly developed water rinse process. The rinse processes that will be discussed will have the flexibility of integrating the surfactant-containing rinse solution while maintaining the shortest possible cycle time. At the same time these processes will reduce defects and pattern collapse.
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.
Development of next generation mask technology requires the use of several different metallic materials. As a result, it is necessary to develop resist processes which offer a combination of good resolution and adhesion for each surface. In this study, Ultra i-300, a high resolution, chemically amplified, negative i-line resist was evaluated for use with several metal substrate materials. The metal films in the evaluation include: Cr, TaSi, TaSiN, and TiW. Early tests with Ultra i-300 using a baseline process optimized for silicon, provide very poor adhesion on these metal films. Several approaches were used to solve this problem including pre-application dehydration bakes, modified processing bakes, surface pretreatments, and use of anti-reflective coatings. Adjustment of the soft bake/post bake temperatures greatly improved adhesion, but resulted in severe standing waves and/or poor processing latitude. Significant improvements were achieved using AR2-600 a DUV anti-reflective coating (ARC) with a modified bake process. This eliminated standing waves, improved adhesion, and provided the best resolution and processing latitude. Other ARCs were also evaluated in an attempt to further optimize the process. Although the goal of this study was to develop a resist process for next generation mask technology, the results are applicable wherever it is desirable to use a negative i-line resists on metallic substrates.