Bottom Antireflective Layer Research Articles

The use of high aspect ratio photoresist (SU-8) for super-hydrophobic pattern prototyping

In this work we present a reliable technique for the production of large areas of high aspect-ratio patterns and describe their use as model super-hydrophobic systems. The high thickness and straight sidewalls possible with SU-8 were used to generate dense patterns of small pillars. These photoresist patterns could be used directly, without the need for micromoulding. A method is given allowing resist thickness to be varied over a wide range and a bottom antireflective layer was used to simplify patterning on reflective substrates. This patterning technique allows rapid testing of wetting theories, as pattern size and depth can be varied simply and samples can be produced in sufficient numbers for laboratory use. We show how the static contact angle of water varies with pattern height for one sample-pattern and how static and dynamic contact angles vary with dimension using high aspect-ratio patterns.

Diluted Low Dielectric Constant Materials as Bottom Antireflective Coating Layers for both KrF and ArF Lithography Processes

In this paper, we report on a bottom antireflective coating (BARC) layer for both KrF and ArF lithography processes. The antireflective layers are composed of diluted low-dielectric constant materials, such as bisbenzo(cyclobutene) (BCB), fluorinated poly(arylene)ether (FLARE) and SiLK. By adding an optimized thickness of diluted low-dielectric constant materials, the reflectance of less than 1% at the resist/silicon substrate interface can be achieved. Diluted low-dielectric constant materials also have great potential to be used as BARC layers on various highly-reflectance substrates for metal-interconnect applications. Using this structure, it is easy to reduce reflectance without adding an extra BARC layer for patterning low-dielectric materials. After the lithography procedure, the diluted low-dielectric constant layer need not be removed.

Low Dielectric Constant Polymer Materials as Bottom Antireflective Coating Layers for both KrF and ArF Lithography

In this paper, we demonstrate a new bottom antireflective coating (BARC) layer for both KrF and ArF lithography. The antireflective layers are composed of a novel low-dielectric constant polymer material (SiLK) and its etching hard-mask layer. By adding an optimized hard-mask layer, the reflectance of less than 1% at the resist/silicon substrate interface can be achieved. SiLK also has great potential to be used as BARC layers on various highly-reflectance substrates for metal-interconnect applications with large thickness-controlled tolerance. By using this novel structure, it is easy to reduce reflectance without adding an extra BARC layer for patterning low-dielectric materials. In this paper, suitable etching characteristics and thermal stability of SiLK-based BARC layers are also described.

Novel antireflective layer using polysilane for deep ultraviolet lithography

A bottom antireflective layer (ARL) is essential for deep ultraviolet (UV) lithography. We have just developed a polysilane antireflective layer (PSARL) process. PSARL can act as an antireflective layer due to the Si–Si bond which has absorption in the deep UV region, and it can be etched with high selectivity to resist under etch conditions that use a chlorine plasma which is a suitable inorganic silicon etchant. Similar to the conventional organic ARL process, PSARL can be simply spin coated onto the substrate, and removed with an asher using an O2/CF4 gas mixture. The partially cross-linked diphenylsilane copolymer was evaluated with a view to its application as an ARL material and the results obtained are presented in this article.

Roles of Surface Functional Groups on TiN and SiN Substrates in Resist Pattern Deformations

Resist pattern deformations on a bottom anti-reflective layer (BARL) are a serious problem for deep UV lithography. To clarify the mechanism of these pattern deformations, we analyzed SiN and TiN substrates (candidates of BARL materials) by Auger electron spectroscopy (AES) and thermal desorption (TDS). We also applied N2 annealing and thermal oxidation to the substrates. To examine the reactivity of the substrates to the acid generated in the resist, the potential energy and partial charges of model compounds were calculated using the molecular orbital method. By comparing experimental and calculational results, it was found that the Si–OH group neighboring N atoms on SiN substrates was a stronger base than the Si–OH group neighboring O atoms. We also found that NHx groups can easily react with the acid. The oxidation of SiN, which eliminates NHx and N–Si–OH, prevented pattern deformation. In the case of TiN, on the other hand, oxidation was not effective because Ti–O–Ti can be decomposed by the acid.

Fluorinated silicon nitride film for the bottom antireflective layer in quarter micron optical lithography

Fluorinated silicon nitride thin film as a bottom antireflective layer (BARL) material, being suitable for line-patterning in KrF excimer laser (248 nm) lithography, has been studied by film fabrication/characterization and computer simulation. Three-dimensional reflectance simulation process suggests that the 0% reflectance between photoresist (PR) and BARL can be achieved by selecting proper combinations of film optical properties such as refractive index (n), extinction coefficient (k) and thickness (d). For the PR/300 Å BARL/c-Si or PR/300 Å BARL/W-Si structure at a wavelength of 248 nm, the simulation process reveals that nearly 0% reflectance could be obtained when the n and k values of the film are 2.109 and 0.68 or 2.052 and 0.592 respectively. The fluorinated silicon nitride films prepared by ICP enhanced CVD have been evaluated with the variations of flow rates under the two conditions of and 3:20 (sccm). The film n and k values at 248 nm vary in the ranges of 1.665 - 2.352 and 0.007 - 0.695 respectively, depending on gas flow ratio. As it is very sensitive to the film thickness, the reflectance could be reduced, using compoter simulation, to almost 0% by changing the film thickness. Furthermore, the ARL performance for line/space processed by the KrF excimer laser stepper and the stripping ability/selectivity show this material to be a superior candidate for deep-UV microlithography applications.

Titanium oxide film for the bottom antireflective layer in deep ultraviolet lithography

Titanium oxide thin film, fabricated with tetraisopropyltitanate and oxygen by electron cyclotron resonance-plasma-enhanced chemical vapor deposition, is investigated as a potential candidate for the antireflective layer in KrF excimer laser (248-nm) lithography. The oxygen flow-rate dependence of the optical properties such as the refractive index (n) and the extinction coefficient (k) of the film at the 248-nm wavelength has been characterized, and the films with the expected combinations of n and k values for the antireflective layer have been deposited. Simulation results indicate that reflectance values of less than 4% and as low as 1.2% can be reached at the interface between the photoresist and the film postulating the structures of the photoresist/300-A TiO(x) film/c-Si substrate and the W-Si substrate, respectively, by selected proper combinations of n and k values. Moreover the reflectance can be further reduced to almost zero by changing the film thickness. Thus it is found that titanium oxide thin films can be used as the bottom antireflective layer in KrF excimer laser lithography.

The Applicability of Fluorinated Silicon Nitride Film As Bottom Antireflective Layer In Deep Ultraviolet Lithography

AbstractThis study describes the use of fluorinated silicon nitride film as a bottom antireflective layer (BARL) material suitable for line-patterning in quarter-micron KrF excimer laser lithography. For the structures of photoresist/BARL (300Å)/c-Si and photoresist/BARL (300 Å )/W-Si at a wavelength of 248nm, 0% reflectance could be achieved when the refractive index (n) and extinction coefficient (k) values of the film are 2.11 and 0.68 or 2.05 and 0.59, respectively. The fluorinated silicon nitride thin films on p-type (100) Si substrates obtained by inductively coupled plasma enhanced CVD have been evaluated with the variations of NF3 flow rates under the two conditions of SiH4:N2=2:15 and 3:20 (seem). The films optical constants and reflectance were investigated by spectroscopic ellipsometry combined with a reflectance simulation program. The film n and k values at 248nm vary in the ranges of 1.67~2.35 and 0.01~0.69, respectively, depending on gas flow ratio of SiH4:N2:NF3. Low reflectance of below 5% can be obtained from reflectance simulation for two deposition conditions with a BARL thickness of 300Å. In addition, the reflectance could be reduced to almost 0% by controlling film thickness. Finally, the antireflective layer performance was investigated using KrF excimer laser lithography.

Bottom anti-reflective coatings: Control of thermal processing

This paper investigates the thermal process conditions of the Bottom Anti-Reflective Layer for i-Line lithography (BARLi) using various characterization techniques such as TGA and WCM (Tg). The thermal modifications of the material are related to the variations in its functional properties, namely degree of solubility, absorption, thickness and reflectivity. A thermal process window is defined to obtain a maximum improvement from this technology.

Characterization Enhancements in Resist Photospeed

Current photospeed testing methods are based on dose to clear or resist contrast . Either method is inadequate for controlling sensitivity to within ±1.5%. We investigated various methods for improving these photospeed tests. Ranked in order of decreasing importance are: (i) controlling standing waves (reflectivity); (ii) choice of developer; (iii) develop time; and (iv) exposure pattern. Reflectivity can be controlled by careful attention to resist thickness, addition of a bottom antireflective layer, addition of a low refractive index layer (AquaTar), or by using a thick photoresist. Moreover, we can utilize the whole dissolution curve rather than the one‐point determination of the test. We have identified regions in the dissolution curve that are highly sensitive measures of change in development rate per change in dose. This test dubbed PS‐50 measures the dose required to achieve 50% film retention of the exposed and developed film. This test with the addition of a bottom antireflective layer has improved test precision.