Pattern Freezing Process Free Litho–Litho–Etch Double Patterning

Abstract

Double patterning technology based on existing ArF immersion lithography is considered as the most viable option for complementary metal oxide semiconductor (CMOS) node of 32 nm and below. Most of double patterning approaches previously described requires intermediate processing step such as hard mask etching, spacer material deposition, and resist pattern freezing. The requirement of these additional steps is now leading way to requests for throughput reduction and low cost for production for double patterning technology applications. In this paper, litho-litho-etch (LLE) double patterning without any intermediate processing steps is investigated to achieve narrow pitch resist imaging. The LLE options examined in this work are combinations of positive tone-negative tone and positive tonepositive tone photoresist double patterning process. These are the alternative processes in pattern freezing process free LLE double patterning. The goals of this work are to determine witch of these approaches is the most viable for future application and to confirm the patterning potential for 32 nm and below half pitch resist imaging.

Newly developed positive tone resists for Posi/Posi double patterning process

“…There was pattern height difference between 1 st and 2 nd resist that was caused by coating topography at 2 nd lithography. If thickness of 2 nd resist is thinner, pattern height should be close [5]. For the smaller contact hole target, 6a716 and PP006 were exposed with 40nm Line and space, then 40nm contact hole 80nm pitch pattern was obtained by using 1.35 NA dipole.…”

“…For contact hole application, cross-line contact hole method becomes to be more discussed and investigated since last year 4,5) . On the other hands, image reverse method is also good candidate to obtain small contact hole.…”

“…But "Posi/Nega" process had resolution issue of negative tone resist because optical contrast for negative tone resist at 1L/3S is quite lower than contrast for positive tone at 1L/3S. [4,5] Thus we introduce "Posi/Posi" Process without freezing process. The "Posi/Posi" process is the simplest process of DPT except double exposure and should be cost helpful process.…”

<title>Layout optimization through robust pattern learning and prediction in SADP gridded designs</title>

“…Consequently, the pattern density is less dense in each mask and the desired resolution can be resolved using the currently available lithography setup. Several major double patterning techniques exist: Litho-Etch-Litho-Etch (LELE) [10], Litho-Freeze-Litho-Etch (LFLE) [1], Self-Aligned Double Patterning (SADP) [3], and Line-End Cut (LEC) [2][4] [11] [12]. LELE splits the design layout shapes of a layer into two separate masks.…”

Advanced patterning solutions based on the "shrink process assisted by double exposure" (SPADE)

“…LLE involves pattern stabilization of the first lithography (L1) images before the second lithography (L2). Numerous techniques have been explored for the resist stabilization including ion implantation, 8 UV curing, 9,10 thermal hardening, 11 thermal curing, 12,13 or chemical curing. 9,[13][14][15] Regardless of the stabilization method employed, it should fulfill three minimum requirements for the successful double patterning: (1) no pattern deformation during the resist stabilization process, (2) no intermixing between L1 and L2 resist layers during the L2 resist coating/soft bake process, and (3) no aqueous base development of L1 patterns during the L2 exposure/develop process.…”