Investigating the structure–sensitivity relationship of photosensitive polyimide formulated by using a photobase generator

Abstract

Photosensitive polyimides (PSPIs) have been widely used in the buffer coating layer and insulation layer due to their excellent thermal and mechanical stability. In this work, a series of negative‐type PSPIs based on poly(amic acid) (PAA) and a photobase generator (PBG) have been developed. Two diamines of 4,4′‐oxydianiline (ODA), 3,3′‐diaminodiphenyl sulfone (SDA), and four dianhydrides of pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA) and cyclobutene‐1,2,3,4‐tetracarboxylic dianhydride (CBDA) are copolymerized to PAA through polyaddition, and the PAA is further thermally imidized to polyimide (PI). Through scrutinizing the structure–sensitivity relationship of these PIs, we find that the rigidity and transparency of the PAA/PI backbone play an important role in the sensitivity and contrast of PSPI. Accordingly, PSPI (SDA‐ODPA), possessing high optical transparency and a low rigidity represented by the low glass transition point, is capable of providing good photosensitivity of 30 mJ/cm2, a high contrast of 2.46, and an excellent pattern resolution of 4 μm after optimizing the prebaking (100°C for 5 min), exposure dose (380 mJ/cm2), post‐exposure baking (130°C for 7 min), and development parameters. This work provides the concept of structural design for negative‐type PSPI in the microelectronic application.

Photopolymerization activated by photobase generators and applications: from photolithography to high-quality photoresists

“…101 For instance, Chang et al found that the high optical transparency and low rigidity of the polyimide backbone give a significant promotion on the performance of PSPI, especially for the photosensitivity, owing to the designed wide optical bandgap and low rigidity are beneficial for the photochemical reaction and chemical imidization. 102 In 2019, Noda et al fabricated nega-type patterns efficiently attained by polysilane solution with optimum ratio of OXTA-P2 t Bu (1.8 : 1) as a PBG under UV irradiation, where the ratio determined by the observations on pH change, ESR and UV absorption spectra, combining with quantum chemical calculation. 17 These work re-confirmed the important role of designs on molecular structures, compositions of the PBGs and monomers, even for the design of fluorescent species, no matter these species are derived from organic molecules or nanomaterials, which could become the mainstream method to expand the family of highly efficient PBGs, further promoting their microelectronic applications, particularly in the photoresist aspect in the future.…”

Preparation and Properties of Low-Dielectric Polyimide Films Containing Tert-Butyl

“…In this context, low-dielectric materials have attracted much interest. Particularly, polyimide (PI) films are considered as one of the most promising candidates for the next generation of dielectrics due to their excellent thermal [6][7][8], mechanical [9,10], and dielectric properties [11][12][13][14][15], and have been applied in insulation layers, buffer coatings, and passivation layers in the microelectronics industry [16][17][18][19]. However, it is a fact that the dielectric constant of most PI films is not low enough (approximately 3.2-4.0).…”

Quaternary copolymerized polyimides and negative photosensitive polyimides: preparation and properties

“…[1][2][3][4][5][6][7][8] Photosensitive polyimide (PSPI) simplifies traditional PI processing. 7,[9][10][11][12][13] The graphic technology of PI has also developed. 14 Fabricating PI pattern becomes more convenient.…”