Shinji Miyazaki

Advanced CD-SEM metrology for pattern roughness and local placement of lamellar DSA

Directed self-assembly (DSA) applying chemical epitaxy is one of the promising lithographic solutions for next generation semiconductor device manufacturing. We introduced Fingerprint Edge Roughness (FER) as an index to evaluate edge roughness of non-guided lamella finger print pattern, and found its correlation with the Line Edge Roughness (LER) of the lines assembled on the chemical guiding patterns. In this work, we have evaluated both FER and LER at each process steps of the LiNe DSA flow utilizing PS-b-PMMA block copolymers (BCP) assembled on chemical template wafers fabricated with Focus Exposure Matrix (FEM). As a result, we found the followings. (1) Line widths and space distances of the DSA patterns slightly differ to each other depending on their relative position against the chemical guide patterns. Appropriate condition that all lines are in the same dimensions exists, but the condition is not always same for the spaces. (2) LER and LWR (Line Width Roughness) of DSA patterns neither depend on width nor LER of the guide patterns. (3) LWR of DSA patterns are proportional to the width roughness of fingerprint pattern. (4) FER is influenced not only by the BCP formulation, but also by its film thickness. We introduced new methods to optimize the BCP formulation and process conditions by using FER measurement and local CD valuation measurement. Publisher’s Note: This paper, originally published on 2 April 2014, was replaced with a corrected/revised version on 14 May 2014. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.

Etching spin-on trilayer masks

Spin-on trilayer materials are increasingly being integrated in high density microfabrication that use high NA ArF lithography due to dwindling photoresist film thicknesses, lower integration cost and reduced complexity compared to analogous CVD stacks. To guide our development in spin-on trilayer materials we have established etch conditions on an ISM etcher for pattern transfer through trilayer hard masks. We report here a range of etch process variables and their impact on after-etch profiles and etch selectivity with AZ trilayer hard mask materials. Trilayer pattern transfer is demonstrated using 1st and 2nd minimum stacks with various pattern types. Etch recipes are then applied to blanket coated wafers to make comparisons between etch selectivities derived from patterned and blanket coated wafers.

Spin-on trilayer approaches to high NA 193nm lithography

New challenges face ArF bottom antireflection coatings (BARCs) with the implementation of high NA lithography and the concurrent increase use of spin-on hard masks. To achieve superior reflectivity control with high NA at least two semi-transparent ARC layers, with distinct optical indices, are necessary to effectively lower substrate reflectivity through a full range of incident angles. To achieve successful pattern transfer, these layers in conjunction with the organic resist, should be stacked with an alternating elemental composition to amplify vertical resolution during etch. This will circumvent the inherent low etch resistance of ArF resist and the decreasing film thicknesses that accompanies increasing NA. Thus, incorporating hard mask properties and antireflection properties in the same two layer system facilitates pattern transfer as a whole rather than just enhancing lithography. As with any material expected to exhibit multiple roles there is a delicate balance between optimizing materials with respect to one of its roles while not impairing its other roles. We will discuss some of these conflicts and present Si-BARCs and carbon rich underlayers which aim to balance these conflicts. In this paper we will explore simulations aimed at finding the best film thicknesses and optical indices, etch rate selectivity, and lithographic performance of high silicon content and high carbon content BARC materials designed to meet the demands of both high NA lithography and trilayer processing.

Latest developments in photosensitive developable bottom anti-reflective coating (DBARC)

Developable bottom anti-reflective coatings (DBARC) are an emerging litho material technology. The biggest advantage of DBARC is that it eliminates the plasma etch step, avoiding damage to plasma sensitive layers during implantation. AZ has pioneered developable BARC based on photosensitive cleave as well as crosslink/decrosslink mechanisms. In this paper, we focus on the crosslink/decrosslink concept. DBARC/resist mismatching was corrected both from process and formulation sides. The optimized DBARC showed comparable lithographic performance as conventional BARCs. This paper provides the chemical concept of the photosensitive developable DBARCs, approaches for DBARC/resist matching and performance of photosensitive DBARCs for 248 nm and 193 nm exposures. Recent 193 nm immersion exposure results are also presented.