The minimum target specificatons of EUV resist material are the resolution < 30nm half pitch C/H, CDU < 3.0nm, and sensitivity < 20mJ. The major pending issue of EUV resist is how to simultaneously achieve high sensitivity, high resolution and low CD Uniformity (CDU). Thus, we have studied that which factors such as acid diffusion, solvents, polymer platform and film density etc are affecting to improve CDU, sensitivity and resolution. Especially, CDU and sensitivity are the main issues among above these performances. With the results of these experiments, we could determine polymer blend PAG as polymer platform for EUV resist material. We have also researched polymer to improve the sensitivity and CDU with variation of molecular weight, poly dispersity and monomer feed ratio. Additionally, we have studied the effects of resist solvents and film density. And we have measured the outgas of our EUV resist. In this paper, we will discuss the results of these studies obtained by EUV tools of SEMATECH.
The minimum target specificatons of EUV resist material are the Resoultion ≤ 22nm half pitch L/S, Line Width Roughness ≤ 1.7nm, and Sensitivity 10mJ~15mJ[1]. The major pending issue of EUV resist is how to simultaneously achieve high sensitivity, high resolution and low LWR.[12] Especially, LWR[2] is the main issue among above RLS performances. Thus, we have measured acid diffusion length of blend type PAG and Polymer bound PAG in order to confirm the fact that the acid diffusion length of Polymer Bound PAG type is shorter than that of blend type PAG. With the results of these experiments, we could determine polymer bound PAG as polymer platform for EUV resist material. We have also researched about acid labile group to improve the sensitivity of EUV resist with introduction of various kinds of monomers and we have tried to develop novel acid amplifier to get a good acid yield. Additionally, we have also studied the effects of steric hinderance through diversifying the size of pendent group to make polymer of high performance. In this paper, we will discuss the results of these studies obtained by EUV tools.
It is well known EUV lithography is the most promising technology for next generation lithography. ITRS roadmap
predicts that EUV lithography will realize 22nm half pitch node and beyond. However, there are a lot of problems such
as light source power, exposure tools, mask blank defect and resist material for realizing of EUV lithography. Among
these problems, we try to develop the high performance resist material for EUV lithography in this paper. EUV resist
material are to achieve the Resoultion ≤ 22nm half pitch L/S, Line Width roughness ≤ 1.2nm, Sensitivity ≤ 10mJ.
The major development issue of EUV resist is how to simultaneously achieve high sensitivity, high resolution, low LWR.
Especially, LWR is the main issue among above RLS performances. So, we decided to choose the polymer bound PAG
as resin platform for EUV resist material. Thus, we have studied in various ways to know the relation between LWR
reduction and resin physical properties which represents substituted ratio of acid-cleavable unit, Mw, Pd. Additionally,
we studied the effects of steric hinderance of pending group with diversifying the size of pending group to make polymer
of high performance. We also attempt to know how is LWR affected by hydroxy group species. In this paper, we will
show and discuss the results of these studies obtained by tools of e-beam and EUV.
The main issue for developing EUV resist is to satisfy the ITRS target of sensitivity, line edge roughness(LER), and
resolution simultaneously. However, Resist researchers have difficulty in EUV resist development because they are
tradeoff relationships each other. Among them, LER is closely related to acid diffusion length of photo acid generator.
Researchers have tried to accomplish uniform distribution and diffusion minimization of PAG in photoresist film in order
to improve LER. They are mainly using two kinds of method for PAG introduction for uniform distribution and diffusion
minimization. One is use of sulfonium salts having ultra bulky anion or cation for the acid diffusion suppression, the
other is direct incorporation of the PAG into the polymer backbone. In that regard, we have pursued development of a
variety of 193nm and EUV CARs that contain photoacid generator(PAG) units covalently bonded directly to the resin
polymer backbone. When we consider polymer bound PAG, there can be anionic polymer bound PAG resist, cationic
polymer bound PAG resist and nonionic polymer bound resist. In this work, we will discuss diffusion length and line
edge roughness(LER) of these polymers. Acid diffusion length(Ld) and diffusion coefficient(D) were calculated by
according to the modified Fick,s equation. As a result of this measurements we knew that diffusion length of general
PAG use as ArF photoresist composition was ranged from thousands of nm to ten of nm and PAG diffusion length having
bulky anion and cation is was within a ten nm. In case of anionic polymer bound PAG, acid diffusion length showed
under 10nm.
One of the most important factors in ArF resist development is a resin platform, which dominates a lot of parts of resist characteristics. It has been much changed in order to improve their physical properties such as resolution, pattern profile, etch resistance and line edge roughness. Through the low etch resistance in ArF initial (meth)acryl type copolymer and low transmittance in COMA type copolymer most researchers were interested in developing of (meth)acryl type copolymer again for ArF photoresist. On the other hand, we have studied various polymer platforms suitable ArF photoresist except for meth(acryl) type copolymer. As a result of this study we had developed ROMA type polymers and cycloolefin-(meth)acryl type copolymers. Among the polymers cycloolefin-(meth)acryl type copolymer has many attractions such as etch roughness, resist reflow which needs low glass transition temperature and solvent solubility. In this study, we intend to find out cycloolefin-(meth)acryl copolymer characteristics compared with (meth)acryl copolymer. And, we have tried to find out any differences between acrylate type copolymer and cycloolefin-(meth)acrylate type copolymer with various evaluation results. As a result of this study we are going to talk about the reason that the resist using acrylate type copolymer and cycloolefin-(meth)acryl type copolymer show good pattern profile while acrylate type copolymer show poor pattern profile. We also intend to explain the role of cycloolefin as a function of molecular weight variation and substitution ratio variation of cycloolefin in cycloolefin-(meth)acrylate resin.One of the most important factors in ArF resist development is a resin platform, which dominates a lot of parts of resist characteristics. It has been much changed in order to improve their physical properties such as resolution, pattern profile, etch resistance and line edge roughness. Through the low etch resistance in ArF initial (meth)acryl type copolymer and low transmittance in COMA type copolymer most researchers were interested in developing of (meth)acryl type copolymer again for ArF photoresist. On the other hand, we have studied various polymer platforms suitable ArF photoresist except for meth(acryl) type copolymer. As a result of this study we had developed ROMA type polymers and cycloolefin-(meth)acryl type copolymers. Among the polymers cycloolefin-(meth)acryl type copolymer has many attractions such as etch roughness, resist reflow which needs low glass transition temperature and solvent solubility. In this study, we intend to find out cycloolefin-(meth)acryl copolymer characteristics compared with (meth)acryl copolymer. And, we have tried to find out any differences between acrylate type copolymer and cycloolefin-(meth)acrylate type copolymer with various evaluation results. As a result of this study we are going to talk about the reason that the resist using acrylate type copolymer and cycloolefin-(meth)acryl type copolymer show good pattern profile while acrylate type copolymer show poor pattern profile. We also intend to explain the role of cycloolefin as a function of molecular weight variation and substitution ratio variation of cycloolefin in cycloolefin-(meth)acrylate resin.
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