In order to prepare for the next generation technology manufacturing, ASML and TEL are investigating the process
manufacturability performance of the CLEAN TRACKTM LITHIUS ProTM-i/ TWINSCANTM XT:1900Gi lithocluster at
the 45nm node. Previous work from this collaboration showed the feasibility of 45nm processing using the LITHIUSTMi+/TWINSCAN XT:1700i. 1 In this work, process performance with regards to critical dimension uniformity and
defectivity are investigated to determine the robustness for manufacturing of the litho cluster. Specifically, at the spinner
and PEB plate configuration necessary for the high volume manufacturing requirement of 180 wafers per hour, process
data is evaluated to confirm the multi-module flows can achieve the required process performance. Additionally, an
improvement in the edge cut strategy necessary to maximize the usable wafer surface without negative impact to defectivity is investigated.
Printing random Contact Holes (C/H) is one of the most difficult tasks in current low-k1 lithography. Different
approaches have been proposed and demonstrated successfully. One approach is the use of extensive Resolution
Enhancement Technique such as sub-resolution assisting features, focus drilling and interference mapping lithography in
combination with strong off-axis illumination. These techniques often lead to enhanced complexity at the OPC and mask
making side. In order to keep the complexity low, soft illumination modes have been proposed like Soft-Annular (bull'seye)
and Soft-Quasar type illumination . It has been shown that the minimum k1 for the latter route is k1=0.41 using
experimental results up to 0.93 NA. In this paper we demonstrate that the latter route can be extended to 45nm C/H at a
minimum pitch of 120nm when using 1.35 NA. In order to achieve this we additionally applied a CD sizing technique to
create the very small C/H.
An impact of air-borne NH3 and humidity against a wafer-to-wafer (WTW) CD variation is investigated. An
environmental stability of ArF resist materials is also investigated through the design of experiment (DOE) analysis,
where the different resist formulations are chosen as variation factors. Assuming the most environmentally sensitive ArF
resist material used in the 45nm 1:1 LS pattern imaging (worst case scenario), the WTW CD variations caused by
air-borne NH3 and humidity fluctuations are estimated to be 0.10nm and 0.29nm, respectively.
Semiconductor manufacturing technology has progressed remarkably in recent years. This progress has been accompanied by demands to reduce the feature size used in photolithography processing, resulting in a reduction of the exposure wavelength from 248 nm (KrF laser) to 193 nm (ArF laser). ArF immersion lithography is now being actively researched and developed with the aim of implementing the 45-nm technology node. Chemically amplified (CA) resists have been introduced to cope with these reduced feature sizes, making it all the more important to reduce defects produced in the lithography process. In recent years, the behavior of defects in a CA resist has been clarified by studies involving various microprobe analysis techniques. Basically, it has been reported that water-soluble defects such as "satellites" and water-insoluble defects such as "resist residues" are generated by various factors. Furthermore, the reduction in pattern sizes has led to the identification of new types of resist-related defects such as "missing-hole" defects in contact-hole (C/H) patterns and "bridging" defects in line-and-space (L/S) patterns. Although the satellite, resist-residue, and missing-hole problems have been addressed by implementing new ideas such as extended rinse times, improved development recipes, and the introduction of post-development rinse stages and improved rinse recipes, it cannot be said that these measures are sufficient in terms of processing throughput or effectiveness. In this paper, we investigate the effect of adding chemical additives to the de-ionized water (DIW) rinse used in the development rinse process. Our studies confirm that these additives significantly reduce the quantity of minute defects generated on the wafer without degrading lithography performance, and thus help to improve process throughput. We also investigate the application of this method to immersion lithography, and confirm that this additive procedure also reduces the quantity of defects in immersion lithography processes.
As the minimum feature size of electronic devices continues to shrink, the industry is moving from 248-nm wavelength KrF excimer laser sources to shorter wavelength 193-nm ArF excimer and 157-nm F2 excimer sources to achieve the higher resolution lithographic processes that are required. This requires optimum control over CD(critical dimension), but also the ability to minimize and reduce device defects is critically important. Satellite defects and various other kinds of defects were found to occur in the development process when chemically amplified resists are used in 248-nm lithography, and these defects clearly have an adverse effect on yields. Now that the industry is moving from KrF (248- nm) to ArF (193- nm) exposure systems, this means the requirements to control and reduce these micro defects are more exacting than ever before. In this paper we describe the generation behavior of defects caused by bottom anti-reflective coating (BARC) and the adherence behavior of defects onto the BARC. In this work we show that the generation behavior of defects is clearly affected by the thickness of the BARC, and the adherence behavior of defects is well explained by potential analysis measurements. With the transition toward shorter wavelength exposure systems, varying the thickness of the BARC is likely to have a major impact on the CD in lithography processes, but controlling the thickness of BARC layers is also extremely important from the standpoint of controlling defects. While we certainly must continue in our efforts to develop better resists that minimum defects, our results suggest that we must also focus attention on optimizing and closely controlling the entire lithographic process.
As the minimum feature size of electronic devices shrinks to less than 0.25 μm, it is critically important that we reduce the defects that occur in lithography processes. Moreover, as the defects to be controlled become ever smaller, this makes them increasingly difficult to detect by conventional fault detection equipment. In order to detect these minute defects in the context of shrinking device geometries, it is essential that we develop a clear understanding of the behavior of micro defects in developer. In principle, there are three ways in which these defects might be dealt with: (1) defects can be prevented from occurring in the first place, (2) defects can be prevented from adhering to the device, or (3) defects can be eliminated after they occur. Our recent work has mainly been concerned with the first and most effective approach of preventing defects from occurring in the first place, and this motivated the present study to investigate the mechanisms by which defects occur. We believe that defects occur in chemically amplified (CA) resists that are insufficiently unprotected at boundary regions between unexposed and exposed areas or in unexposed areas, so that the de-protection reaction in the resist suns to different degrees of completion due to varying exposure doses. In this study we investigate the number of defects in various developers, and determine the size distribution of the defects. Based on analysis of the behavior of defects from their size distribution in develop we conclude that: (1) the size of defects increases when the exposure dose is reduced by appropriate Eops, (2) defects originate in the boundary area between unexposed and exposed areas, and (3) a portion of CA resist polymer that is insufficiently deprotected is dispersed in the developer, coalesces and is deposited in a form that is not very soluble, and is manifested as relatively large particle defects.
In this study, we investigated resist pattern collapse during the resist development process. We evaluated the effect of a simple improvement such as rinse-liquid sequencing and rinsing using surfactants. First, we controlled the wafer spinning speed during the rinse-liquid flow step to reduce liquid flow shock. Using this approach, we obtained a 110-nm L/S (line and space) structure with no pattern collapse. However, this technique has only a small effect on preventing pattern collapse with sub-100-nm devices. By using a rinse process with a surfactant, we could control pattern collapse with 100-nm L/S or smaller patterns. Finally, we have succeeded in controlling pattern collapse of 70-nm L/S patterns (aspects ratio of 4.6) using a surfactant during the rinse process. These two simple methods are a significant improvement over conventional rinse processes. These process improvements are available for 90-nm (and smaller) design rules and are applicable for a single layer resists.
Reduction of critical dimension in lithography technology is aggressively promoted. At the same time, further resist thickness reduction is being pursued to increase the resolution capabilities of resist. However, thin film has its limitation because of etch requirements etc. As that result, the promotion of reduction results in increasing the aspect ratio, which leads to pattern collapse. It is well known that at drying step in developing process the capillary effect operates the photoresist pattern. If the force of the capillary effect is greater than the aggregation force of the resist pattern, the pattern collapse is generated. And the key parameters of the capillary effect are the space width between patterns, the aspect ratio, the contact angle of the D.I water rinse and the surface tension of rinse solution. Among these parameters the surface tension of rinse solution can be controlled by us. On the other hand, we've already reported that the penetration of TMAH and D.I water into the resist plays an important role on the lithographic latitude. For example, when we use the resist which TMA ion can be easily diffuse into, D.I water and TMA ion which are penetrated in the resist decreases the aggregation force of resist pattern and causes the pattern collapse even by the weak force against resist pattern. These results indicate that the swelling of photoresist by TMA ion and water is very important factor for controlling the pattern collapse. Currently, two methods are mainly tried to reduce the surface tension of rinse solution: SCF (Super Critical Fluid) and addition of additive to D.I water rinse. We used the latter method this time, because this technique has retrofittability and not special tool. And in this evaluation, we found that the degree of suppressing pattern collapse depends on the additive chemistry or formulation. With consideration given to process factors such as above, we investigated what factors contribute to suppressing pattern collapse for each resist platform when using additive-added rinse solutions. This report describes the results of our examinations and discussions of the pattern collapse mechanism.