In this work, the authors explore the application of tetramethylammonium hydroxide (TMAH) developer chemical as a staining agent to enhance the top-down contrast of a silylated pattern to optical detection. When examining a silylated latent image top-down, the topographical differences generated due to the swelling of the silylated region are relied upon to identify pattern details. However, for lower exposure energy or shorter silylation times, there may not be sufficient silicon incorporation to allow clear identification of specific structures for cleaving. The authors have used the TMAH staining technique proposed by La Tulipe et al. to enhance the relief top-down, thereby facilitating analysis of even mildly silylated samples. Results will be presented illustrating the contrast enhancement after staining. Cross-sections of film profiles after aqueous silylation of an I-line photoresist with a solution of hexamethylcyclotrisilazane will also be generated.
Top Surface Imaging (TSI) is a well-established technique used to improve resolution for optical, ultraviolet and electron-beam lithography. The Positive Resist Image by Dry Etching (PRIME) is an advanced lithographic process incorporating electron beam exposure, near UV flood exposure, silylation and dry development. In this paper, the liquid-phase silylation process step in PRIME with Shipley SPR500A-series resists has been experimentally investigated as the most critical part of the process. FT-IR spectroscopy, UV spectroscopy, SIM spectrometry and cross-sectional SEM and TEM were used to characterise the silylation process. Electron-beam exposure with dose in the range of 25-100μC/cm2 at 30KeV was used to crosslinks the resist. Results show that an e-beam dose of 50µC/cm2 was sufficient to prevent silylation in the crosslinked areas. Two bifunctional silylating agents, the cyclic Hexamethylcyclotrisilazane (HMCTS) and the linear Bis[Dimethylamino] dimethylsilane (B[DMA]DMS), were examined and found that they silylate SPR505A much more efficiently than the previously reported Hexamethylcyclotrisiloxane (HMCTSx). The silylation contrast of the PRIME process using HMCTS silylating agent and SPR505A resist was found to be 11:1. The obtained silylated profiles of 1mm lines/spaces gratings for Shipley SPR510A resist have almost vertical sidewalls resulting in very high contrast between the silylated and unsilylated parts of the resist.
KEYWORDS: Diffusion, Silicon, Finite element methods, Process modeling, Photoresist processing, Chemical elements, Data modeling, Photomasks, Silicon films, Computer simulations
In this work, a new 2D resist silylation simulator called STIL II has been developed. This simulator extends the 1D methodologies used in the STIL simulator to two dimensions. The silylation process is modeled asa 2D initial boundary value problem, using Fick's Diffusion Equation to describe the diffusion of the silylating agent, which is then solved using in-house written Finite Element Analysis code. This model comprehends the balance of diffusion and reaction rates in the silylation process due to swelling of the resist film. The swelling effect itself, is modeled as a boundary movement problem with the boundaries, and therefore size, of each 2D element being modified in proportion to the silicon concentration in that region. The output of the STIL II simulator is then applied to previously published experimental dat. STIL II predictions agree well with mask center and mask edge silylation thickness experimental results for an I-line scheme. Silylation contrast has ben sued as an indicator to demonstrate the robustness of silylation processing to defocus effects.
KEYWORDS: Diffusion, Silicon, Photomasks, Photoresist processing, Finite element methods, Chemical elements, Process modeling, Data modeling, Computer simulations, Lithography
In this work, a new resist silylation simulator called STIL has been developed. This simulator models the silylation process as a 1D Initial Boundary Value problem which is then solved using in-house developed Finite Element Analysis code. In this model, the silylating agent diffusion and reaction rates are recalculate dafter each silylating time- step, (delta) t. The swelling mechanism is modeled as a Boundary Movement problem whereby the swelling in each element is a function of the local silicon concentration in that element. By solution of this system across the exposed area, a 2D profile of the silicon concentration is determined over an exposed linewidth. the simulations from this model are compared to published experimental data.
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