Mechanistic Advantages of Organotin Molecular EUV Photoresists

Abstract

The Extreme Ultraviolet(EUV)-induced radiation exposure chemistry in organotinoxo systems, represented by the archetypal [(R Sn) 12 O 14 (OH) 6 ](A) 2 cage, has been investigated with density functional theory. Upholding existing experimental evidence of Sn-C cleavage dominant chemistry, computations have revealed either electron attachment or ionization can single-handedly trigger tin-carbon bond cleavage, partially explaining the current EUV sensitivity advantage of metal oxide systems. We have revealed that tin atoms at dierent parts of the molecule react dierently to ionization and 1 electron attachment, and have identied such selectivity as a result of local coordination chemistry instead of the macro geometry of the molecule. An ionizationdeprotonation pathway has also been identied to explain observed evolution of anion conjugate acid upon exposure and anion mass dependence in resist sensitivity.

Insight into the evolution upon ionization from tin-oxo cage photoresist and counterions by DFT calculation

“…But the affections from counterions could be negligible for the carbon–tin bond energy. Our conclusion is consistent with former reports, 19,22,23 which certify that our calculation is reasonable at this functional and basis set level.…”

“…The photochemical character and property of the cage have been investigated in many studies. 2,[19][20][21][22][23][24] It is commonly accepted that the cleavage of the carbon-tin bond to generate a tin free radical is the first step in the reaction for solubility switching, and the radical species can be confirmed using mass spectrometry. 19,20 Moreover, the carbon-tin bond in the side and belt region presents different chemical properties.…”

Induced Chemical Networking of Organometallic Tin in a Cyclic Framework for Sub-10 nm Patterning and Interconnect Application

“…Recent chip fabrication technology is progressing toward the fabrication of 5 nm node or below with the help of extreme ultraviolet lithography (EUVL) . Hence, the era demands single-nanometer technological nodes which further require suitable resist materials that can print features at sub-10 nm regime through a single exposure, although their development is truly challenging. − In recent times, resist compositions comprising inorganic or organometallic species with resolution potential at the single-nanometer regime and high etch resistance capabilities even with thickness below 20 nm have drawn special attention. − For sub-10 nm patterning applications, it is desirable that the film thickness should be less than 20 nm to avoid pattern collapse. , Also, developing an understanding of the mechanistic aspect of polarity switching of inorganic resist during exposure is an important area as it helps in designing new resist platforms with better performance at a single nanometer regime. − Among various types of inorganic resists, some tin-based compositions are being considered to have the potential to meet the current demand. ,,− In reality, some spin-on type tin-based inorganic resist formulations have been proven to have potential for advanced node applications. , Moreover, as per the recent developments, a few inorganic resists have been shown to have true potential for patterning at a single nanometer regime with a very good pattern profile. − However, the number of such materials is truly limited. Herein, we demonstrate the potential of an organotin-based cage-like network (Sn–CT) as an inorganic resist system for sub-10 nm patterning (Figure ).…”

“…Herein, we demonstrate the potential of an organotin-based cage-like network (Sn–CT) as an inorganic resist system for sub-10 nm patterning (Figure ). In general, at the developmental phase, the resists for EUVL are often screened initially with electron beam lithography (EBL) and helium ion beam lithography (HIBL) to evaluate the patterning potential. − ,− …”

Macrocycle Network-Aided Nanopatterning of Inorganic Resists on Silicon

“…While organic polymeric chemically amplified resists have been the workhorses for the semiconductor industries over the past several decades, it seems that these resists have reached their resolution limit and may not be suitable for patterning desirable low size nodes to meet the current demand of semiconductor industries. , Also, for patterning well-resolved sub-12 nm features, the resist film thickness is desirable to be less than 20 nm. , This is the point where organic resists suffer as they have weak tolerance to etch conditions at this low thickness. , To address these issues, efforts are being directed to develop interesting resist platforms for low node patterning. Among different types of resists, in recent times, inorganic resists have been reported to be the most promising candidates as they offer sub-12 nm patterns with low film thickness and show good etch resistance under common etch conditions. ,− In this context, tin-based inorganic resists among the several other types have gained considerable attention. ,− However, shrinkage of resist films during exposure and baking conditions has been a serious problem for inorganic resists, and therefore, it is a challenge to address the concerning shrinkage issue. Hence, approaches to mitigate this issue are highly desirable, although quite challenging.…”