Margareta Paunescu

Directed self-assembly of topcoat-free, integration-friendly high- x block copolymers

To extend scaling beyond poly(styrene-b-methyl methacrylate) (PS-b-PMMA) for directed self-assembly (DSA), high quality organic high-x block copolymers (HC series) were developed and applied to implementation of sub-10 nm L/S DSA. Lamellae-forming block copolymers (BCPs) of the HC series showed the ability to form vertically oriented polymer domains conveniently with the in-house PS-r-PMMA underlayers (AZEMBLY EXP NLD series) without the use of an additional topcoat. The orientation control was achieved with low bake temperatures (≤200 °C) and short bake times (≤5 min). Also, these process-friendly materials are compatible with existing 193i-based graphoepitaxy and chemoepitaxy DSA schemes. In addition, it is notable that 8.5 nm organic lamellae domains were amenable to pattern development by simple dry etch techniques. These successful demonstrations of high-x L/S DSA on 193i-defined guiding patterns and pattern development can offer a feasible route to access sub-10 nm node patterning technology.

Chemically amplified hybrid resist platform for i-line applications

Three polymer platforms based on acid labile blocked novolaks were investigated. The first, blended with Polyhydroxystyrene/ t-butylacrylate (PHSC), produced incompatible blends for the most part. Compatible blends were obtained for the second platform by reacting novolak and PHSC together with alkylvinylether, which was optimized for resist performance on Cu substrate at and below 10 μm film thickness. The third platform, based on a modified novolak resin, achieved greater than 5 aspect ratio in 25 μm thick films.

Chemically amplified thick film i-line positive resist for electroplating and redistribution applications

Adapting chemically amplified (CA) resist technology to thick film applications is demonstrated in this paper over a wide range of thicknesses and types of substrates. Substantial performance differences were observed over copper (Cu) substrates compared to silicon (Si). These differences are attributed to different photo acid generator (PAG) distribution in the resist depth influenced by its structure and the nature of the substrate. Optimized resist formulations were developed to provide acceptable performance on Cu wafers. A family of new chemically amplified thick film resist products is being introduced to the market. This technology offers significant advantages in throughput and performance over conventional novolak / diazonaphthoquinone (DNQ) products at a competitive cost.

Directed self-assembly materials for high resolution beyond PS- b -PMMA

To extend directed self-assembly (DSA) of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) for higher resolution, placement accuracy and potentially improved pattern line edge roughness (LER), we have developed a next-generation material platform of organic high-χ block copolymers (“HC series”, AZEMBLYTM EXP PME-3000 series). The new material platform has a built-in orientation control mechanism which enables block copolymer domains to vertically selforient without topcoat/additive or delicate solvent vapor annealing. Furthermore, sub-10 nm lines and spaces (L/S) patterning by two major chemoepitaxy DSA, LiNe and SMARTTM processes, was successfully implemented on 12” wafer substrates by using the PME-3000 lamellar series. The results revealed that the new material platform is compatible with the existing PS-b-PMMA-based chemical prepatterns and standard protocols. We also introduced the built-in orientation control strategy to the conventional PS-b-PMMA system, producing a new generation of PS-b-PMMA materials with facile orientation control. The modified PS-b-PMMA (m-PS-b-PMMA) performed LiNe flow DSA yielding a comparable CD process window with improved LER/LWR/SWR after the L/S patterns were transferred into a Si substrate.

A study on post-exposure delay of negative tone resist and its chemistry

Exceptional post exposure delay (PED), CD stability, up to 72 hours was reported. This study was conducted using two negative resist formulations identical in their composition except for their PAG type. A mechanism by which the photoacid is protected from relatively moderate levels of airborne amines is proposed. Evidence of room temperature interaction between the resist components and the acid during post exposure delay was also suggested. Therefore, the PED outcome could be the result of two opposing mechanisms.

Performance comparison of negative resists for copper rerouting and other electroplating applications

Two types of chemically amplified (CA) negative resists were compared lithographically. An acid catalyzed resist and a photopolymerizable type resist. The optimum lithographic performance of the acid catalyzed resist on Cu is in the thickness range below 15μm, with vertical profiles. This resist exhibits inverted profiles on Cu above 15μm of thickness. The Photopolymer type resist performs best above 25μm thickness, and can be used for 120μm thick applications with single coat. Top line rounding is more observed with this resist as its applied thickness is reduced below 20μm. This effect is believed to be related to oxygen uptake in the resist surface. Thus it has a more pronounced effect at relatively thinner films. Both resists are compatible with the electroplating process.

PAG distribution and acid thermal diffusion study in ultra-thick chemically amplified resist films

The introduction of chemically amplified (CA) resist technology to thick films, 10 to 100 um in thickness introduced a number of behavior differences not experienced in thinner films to the same magnitudes. Resist image profile deformation, insensitivity to standing waves and the reduction in polymer deblocking temperatures are significantly affected in thick films to a larger extend than in thinner films. The major contributing factors to these differences are discussed in this paper: 1) the influence of photo-acid generator (PAG) structure on its distribution in resist depth on Cu substrates and 2) thermal acid diffusion, influenced by greater amounts of retained solvents in thick films than in thinner films.