Molecular Glass Resists Based on 9,9′-Spirobifluorene Derivatives: Pendant Effect and Comprehensive Evaluation in Extreme Ultraviolet Lithography

Abstract

A series of molecular glass compounds (SP-BOC, SP-AD, and SP-BU) based on 9,9′-spirobifluorene backbone with different kinds of pendant groups (t-butyloxycarbonyl, adamantyl ester, and t-butyl ester groups) were synthesized. The thermal analysis of the compounds indicated that no apparent glass transition temperature (T g) was observed before the onset of the thermal decomposition temperatures (T d) up to 150 °C. The good thermal resistance suggests that they can satisfy the lithography process and are candidates for photoresist materials. They were used as positive photoresists by mixing with minor components of photoacid generators and other additives, respectively. The amorphous films on the silicon substrate were obtained by spin-coating of the photoresists. The extreme ultraviolet (EUV) performance on the films was evaluated by using soft X-ray interference lithography. The SP-BOC resist achieves the most excellent patterning capability down to 22 nm lines with a line-edge roughness (LER) of 3.3 nm. The outgassing amounts (N s ) of SP-BOC, SP-AD, and SP-BU resists are 3.1 × 1015, 2.3 × 1014, and 2.0 × 1014 molecule/cm2, respectively, at exposure dose of ∼20 mJ/cm2. The results of etch resistance are in the order of SP-AD (0.5 nm/s) > SP-BU (0.8 nm/s) > PMMA (1.1 nm/s) > SP-BOC (1.6 nm/s) > Si 3 N 4 (1.8 nm/s). All the results indicate a significant pendant effect on pattern ability, etching durability, and outgassing for SP resists. This study will help us to understand the relationship between the pendant structure and the EUV lithography and supply useful guidelines for designing molecular resists.

Molecular Glass Resists Based on Tetraphenylsilane Derivatives: Effect of Protecting Ratios on Advanced Lithography

“… 42 Actually, the outgassing of the molecular glass resist such as the spirobifluorene (SP-BOC) resist has been measured, suggesting that the molecular glass with eight t -Boc protecting groups gives an amount of 3.1 × 10 15 molecules/cm 2 at an exposure dose of ∼20 mJ/cm 2 . 23 It is speculated that the outgassing of the TPSi-Boc 70% resist would be smaller than that of the SP-BOC resist because reducing the number of protecting groups in molecules is expected to lead to a lower outgassing amount. 43 The EUV lithographic performances demonstrate that the TPSi-Boc 70% resist has the potential to be used in the semiconductor industry as EUV resist materials for the high resolution, sensitivity, and low LER.…”

“… 19 − 22 They combine both the merits of polymers and small molecules, such as monodispersity, amorphous character, high thermal stability, good compatibility with additives, and small dimensions. 19 − 21 , 23 , 24 Combined with the concept of chemically amplified resists, molecular glass resists are expected to break through the trade-off of RLS (resolution, LER, and sensitivity). 23 − 25 Up to now, most positive-tone MG resists are developed based on polyphenolic cores or rings with 100% protection of acid-labile groups.…”

“… 19 − 21 , 23 , 24 Combined with the concept of chemically amplified resists, molecular glass resists are expected to break through the trade-off of RLS (resolution, LER, and sensitivity). 23 − 25 Up to now, most positive-tone MG resists are developed based on polyphenolic cores or rings with 100% protection of acid-labile groups. However, previous reports 26 − 28 and our recent research 23 , 24 demonstrated that MGs with complete protecting groups were unfavorable for high-resolution patterns.…”

“… 23 − 25 Up to now, most positive-tone MG resists are developed based on polyphenolic cores or rings with 100% protection of acid-labile groups. However, previous reports 26 − 28 and our recent research 23 , 24 demonstrated that MGs with complete protecting groups were unfavorable for high-resolution patterns. The excessive hydrophobicity of MGs may result in the defect of resist films, 26 a poor adhesion to the substrate, 27 and high density of blobs in patterns.…”

Negative-tone molecular glass photoresist for high-resolution electron beam lithography

“…The critical dimension (CD) of the integrated circuit ranges from micrometre, submicrometre to nanometre. At the same time, the corresponding photoresists have also been studied and developed [9][10][11][12][13][14][15][16].…”