A novel positive‐type photosensitive polyimide based on soluble block copolyimide showing low dielectric constant with a low‐temperature curing process

Abstract

A soluble block copolyimide (Bco-PI) was prepared by direct one-pot polycondensation of 2,2-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and cyclohexane-tetracarboxylic dianhydride in the presence of ␥-valerolactone and a pyridine catalyst system using ␥-butyrolactone as the solvent. The thermal transmission temperature (T g ) of Bco-PI was 282°C. By having the curing process occur at 250°C, which was below the T g , colorless and transparent films could be obtained. The film showed excellent optical characteristics. Such properties could not be attained by the conventional high-temperature thermal imidization process of poly(amic acid). The hydroxy groups in the polyimide backbone gave the Bco-PI the potential to become alkaline. To the Bco-PI was added 15 wt % ester of 2,3,4-trihydroxybenzophenone with 1,2-naphthoquinone-(2) diazide-5-sulfonic acid (NT200) as the photoreactive compound. The system worked as a positive-type photosensitive polyimide (PSPI). The sensitivity and contrast of the PSPI system were 220 mJ/cm 2 and 1.27, respectively, when exposed to UV light, followed by development with a 5% tetramethylammonium hydroxide (TMAH) aqueous solution at room temperature. After curing at 250°C for 1 h, the average refractive index of Bco-PI with and without NT200 was 1.5543 and 1.5563, and the optically estimated dielectric constant of the polyimides was 2.66 and 2.67, respectively.

Soluble Polyimides Based on Long-chain Alkyl Groups via Amide Linkages

“…51 In this paper, the synthesis and characterization of a novel series of soluble polyimides, that are based on N-alkyl-3,5-diaminobenzamide (ADBA-X, X = carbon numbers of alkyl chain) having long-chain alkyl groups with 9-14 carbon atoms, and the polyimides based on N-(3,5-diaminophenyl)-3,4,5-tris(alkoxy)benzamide (DPABA-X, X = carbon numbers of alkyl chain) are described. Although polyimides based on ADBA having 4,6,8,10,12,14,16 carbon atom have already been reported, 37,41 the structure-properties relationships of polymers were not investigated thoroughly. The effect of ADBA bearing long-chain alkyl groups via amide linkage for the enhancement of solubility was compared with a series of functional diamines having long-chain alkyl groups reported from our laboratory such as AODB, ADBP and DBAE.…”

Iodine‐Induced Solvothermal Formation of Viologen Iodobismuthates

“…Low dielectric constant materials (low‐ k materials) are useful for the modern semiconductor industry,16 and most low‐ k materials are based on inorganosilica17 and organosilica18 complexes, aromatic polymers,19 fluorinated polymers,20 polyimides,21 low‐dimensional nanomaterials22 and copper and aluminum composites 23. Few studies have explored the dielectric properties of pyridinium iodobismuthates.…”

“…Signif-icantly, the conductivity behaviour of bulk BiI 3 is better than those of 1-4, which is in accord with results derived from the optical diffuse-reflection measurements. Low dielectric constant materials (low-k materials) are useful for the modern semiconductor industry, [16] and most low-k materials are based on inorganosilica [17] and organo- [18] complexes, aromatic polymers, [19] fluorinated polymers, [20] polyimides, [21] low-dimensional nanomaterials [22] and copper and aluminum composites. [23] Few studies have explored the dielectric properties of pyridinium iodobismuthates.…”

Recent Progress of Photosensitive Polyimides

“…By their further investigation, the transparency of the PSPI film strongly depended on the thermal treatment temperatures. 26 Since the polymer was chemically imidized invalerolacton/pyridine mixture at 180 C, no thermal imidization was generally required after the patterning process. However, post curing at lower temperature than glass transition temperature (T g ) induced higher transparency of the resulting PI film compared to that cured at higher temperature than T g .…”