Directed self-assembly (DSA) has the potential to extend scaling for both line/space and hole patterns. DSA has shown the capability for pitch reduction (multiplication), hole shrinks, CD self-healing as well as a pathway towards line edge roughness (LER) and pattern collapse improvement [1][2][3][4]. The current challenges for industry adoption are materials maturity, practical process integration, hardware capability, defect reduction and design integration. Tokyo Electron (TEL) has created close collaborations with customers, consortia and material suppliers to address these challenges with the long term goal of robust manufacturability.This paper provides a wide range of DSA demonstrations to accommodate different device applications. In collaboration with IMEC, directed line/space patterns at 12.5 and 14 nm HP are demonstrated with PS-b-PMMA (poly(styrene-b-methylmethacrylate)) using both chemo and grapho-epitaxy process flows. Pre-pattern exposure latitudes of >25% (max) have been demonstrated with 4X directed self-assembly on 300 mm wafers for both the lift off and etch guide chemo-epitaxy process flows. Within TEL's Technology Development Center (TDC), directed selfassembly processes have been applied to holes for both CD shrink and variation reduction. Using a PS-b-PMMA hole shrink process, negative tone developed pre-pattern holes are reduced to below 30 nm with critical dimension uniformity (CDU) of 0.9 nm (3σ) and contact edge roughness (CER) of 0.8 nm (3σ). To generate higher resolution beyond a PS-b-PMMA system, a high chi (χ) material is used to demonstrate 9 nm HP line/ space post-etch patterns. In this paper, TEL presents process solutions for both line/space and hole DSA process integrations.
The growth mechanism of the passivation layer in the cryogenic process used for silicon deep etching is explored experimentally in an inductively coupled plasma reactor. In particular, the role of SiF4 etching by-products on the SiOxFy layer deposition is investigated. The deposition of a SiOxFy layer using SiF4 and O2 gases is studied by in situ ellipsometric spectroscopy in different experimental configurations to devise the deposition mechanism: SiF4/O2 plasma mixture, alternation of SiF4 plasma and O2 plasma steps and alternation of SiF4 flow without plasma and O2 plasma steps. The refractive index and the thickness of the deposited layer are measured for different substrate temperatures, from −125 °C to 20 °C. Although some of the passivation layer is removed during the wafer warm up, a residual amount remains at the surface. The deposited SiOxFy layer forms more efficiently at low temperature with an optimal temperature of −100 °C in our experimental conditions. The passivation layer was etched by a SF6 plasma without bias versus the deposition temperature, to evaluate its resistance to plasma etching steps. The passivation layer was analyzed by ex situ EDX and XPS. We investigated the role of SiF4 low temperature physisorption in the formation of the passivation layer on the sidewalls of the features that are being etched, which are not submitted to ion bombardment. It is shown that physisorption of SiFx species play an important role because their residence time at the surface is longer, thus increasing the probability of reaction with oxygen.
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