Papers by Keyword: HF

Abstract: Advance nanoscale patterning technology requires high resolution lithography, from ultraviolet (UV, i-line system) to deep ultraviolet (DUV, KrF system) until extreme ultraviolet (EUV), but the compatibility study of new resist types and wet etchant is lacking. The compatibility is defined as the duration of a photoresist being able to withstand in wet oxide etchant. Poor compatibility has potential resist lifting and/or penetration during wet etch process, which causes electronic device performance drifting. Currently, wet oxide etching is widely used in the gate oxide wet etch using patterned resist, as well as in the backside oxide removal with blanket resist front-side coverage. In this paper, we explore the compatibility and understand the impact factors, based on commonly used resist (i.e., KrF and i-line system resist) and wet etch chemicals (i.e. HF based etchant) in industry. It is important to do a quick and straightforward compatibility check before we implement new resists on actual product wafers, to prevent poor compatibility caused resist lifting and/or penetration during wet etch process. Based on oxide thickness check and resist lifting phenomena, it is found that resist baking condition, resist polymer type, resist composition, and lag time from resist coating to wet oxide etching all will affect the compatibility between HF based etchant and resist.

Abstract: In semiconductor device manufacturing, it is often necessary to process devices that incorporate both Si₃N₄ and SiO₂ with etching solutions. Recently, we found that a cellulose-based polymer (DC01) selectively adsorbs onto silicon nitride and acts as a protective film against etching with buffered fluoric acid. However, the mechanism behind this selective adsorption remains unclear, and a protective film persists after etching. QCM measurements and calculations of the surface free energy indicate that the affinity between DC01 and Si₃N₄ was significantly stronger than that of SiO₂. Notably, the same behavior was not observed with cellulose or cellulose acetate, indicating that this phenomenon is unique to our original cellulose. Additionally, we successfully prepared films using a facile dipping method. Furthermore, we discovered that the strongly adhesive DC01 film can be completely removed by subjecting it to oxidative conditions, such as SC-1 or SC-2.

Abstract: Fluorinated chemistries can lead to severe corrosion damage towards silicon and germanium based materials when wafers have a significant amount of electrostatic charges. This corrosion is evidenced on both single wafer and batch tools. It can be prevented by the presence of enough light, and wafer charging can also be eradicated by photo emission with UV light.

Abstract: Post impact microstructural characteristics of 7.62 armour pearcing incendiary bullet was studied on AISI 4340 multilayerd welded joints. The potential application of AISI 4340 steel is found in the construction of combat vehicles using welding process. The welded joints are expected to offer better ballistic resistance like unwelded parent metals in combat vehicles. The traditionally used austenitic stainless steel welding consumables and the transformation effects of the welding process result in inferior ballistic performance of AISI 4340 steel welded joints. Published information revealed that a few attempts were made to successfully resist the bullets at multi layered weld metals by depositing a hard-facing interlayer between traditionally used austenitic stainless steel filler metals and a austenitic stainless steel buttering layer in between the parent metal and the hard – facing interlayer. This paper reports the pre-impact and post-impact microstructural characteristics of multi layered sandwiched joints made of a austenitic stainless steel root, a chromium carbide hard – facing middle layer and a low hydrogen ferritic capping front layer. The effect of the low hydrogen ferritic front layer on the ballistic performance after impact is studied in detail.

Abstract: The served harsh environment of advanced aircraft engine puts forward higher requirements for high temperature titanium alloy performance. The optimized heat treatment technology provides effective theoretical basis for improving the microstructure and properties of high temperature titanium alloys. In this paper, we study the influence of different heat treatment systems on microstructure and mechanical properties of high temperature alloy with equiaxed structure, in order to obtain the corresponding relationship between the process and the microstructure performance of the alloy and the optimal heat treatment process. Analysis the effect of solution treatment on the primary α phase quantitatively by optical microscope and Image-Pro-Plus 6.0 software based on the forged high temperature titanium alloy in α+β phase region. Observe the precipitation of α2 phase and silicide by TEM, optimize the aging process according to hardness test. The results show that the content of primary a phase decrease from 63.3% at 920°C to 15.3% at 990°C with the increase of solution temperature. When the temperature rises to 980~990°C, the structure changes from equiaxed structure to α+β duplex microstructure. And change into lamellar structure when the solution temperature raise to 1010°C. The secondary α phase precipitates more fully when the aging temperature increases. And with increasing aging time, the trend of α2 phase growth become more significantly. The optimum heat treatment system obtained in this experimental is 990°C/1h/AC+700°C/5h/AC, and the α phase is about 15.3%. Hence, the excellent microstructure and properties match has been obtained.

Abstract: For horizontally stacked nanowires or-sheets to compete with finFET, the development of a robust inner spacer module is essential. These inner spacers are required to reduce the parasitic capacitance due to the overlap between the source/drain and gate regions. Here we propose an inner spacer integration scheme for Si gate-all-around (GAA) taking advantage of the selective oxidation and oxide removal of SiGe versus Si. Compared to thermal oxide, we found a very high SiGe-oxide etch rate in aqueous HF solutions. When using an NH₃/NF₃ remote plasma, a reduction in etch rate was found for SiGe-oxide versus thermal oxide. We show Si_0.75Ge_0.25-oxide meets inner spacer requirements for leakage current and electrical breakdown field and finally demonstrate the proposed inner spacer integration scheme using a fin-shaped SiGe/Si multilayer topological-test-structure.

Abstract: Still nowadays in integrated circuits manufacturing, few materials patterns are defined by a wet etch on patterned deep UV photoresist. From dies to dies generation, an optical performance improvement is required, hence an evolution with thinner and thinner positive resist. This makes these latter more sensitive to wet chemical etchant through the polymer, reducing their protection of the underneath material. Following characterizations enable a clear understanding of BHF (Buffered HF) benefits versus diluted HF during a gate oxide definition.

Abstract: Airborne Molecular Contamination (AMC) concentrations become critical during queue-time (between two successive process steps) when wafers are degassing inside Front Opening Unified Pod (FOUP), a confined environment [1]. In that case, AMC concentrations can reach maximum level.

Abstract: Semiconductor manufacturing technologies have developed to the point where molecules, such as water, oxygen and airborne molecular contaminants (AMCs), have become detrimental in specific process conditions. Front Opening Unified Pods (FOUPs) are designed as controlled microenvironments (MEs) that protect processed wafers from AMCs during storage and transport. However, it has been demonstrated that FOUPs are able to accumulate by sorption molecules outgassed by processed wafers. Such contaminants are then able to be subsequently released and transferred to other sensitive wafers leading to detrimental impact [1,2]. This cross-contamination scheme from FOUP to wafer was evidenced especially for volatile acids such as HF or HCl and is responsible of yield losses due to drastic corrosion issues or crystal growth on Cu, Al or TiN materials [1,3,4]. These cross contamination issues can be reduced or controlled using low sorption and outgassing polymer materials as previously reported [4,5]. Another AMC control measure is to purge the FOUP with a dry gas. This provides several advantages, for example, wafers are not easily oxidized thus preventing oxide layers, deposition of hydrocarbons and metal defects [6] However, there is no measured information about the purge impact has on AMC control inside a FOUP. The purpose of this paper is to show and quantify what effect two different FOUP polymers using nitrogen and clean dry air (CDA) purge have on the HF volatile acid control through the Cu-wafers storage.

Abstract: The specimens of single crystal superalloy DD6 with 0.10% Hf and 0.47% Hf were prepared in the directionally solidified furnace. The effect of Hf content on the isothermal oxidation resistance of the second generation single crystal superalloy DD6 was studied at 1000°Cin ambient atmosphere. Morphology of oxides was examined by SEM, and their composition was analyzed by XRD and EDS. The experimental results show that the oxidation resistance of DD6 alloy with 0.47% Hf is better than that of the alloy with 0.10% Hf. The alloy with different Hf content all obeys parabolic rate law during oxidation for 100h at 1000°C. The increase of Hf content can promote the Al₂O₃ formation and decreases the proportion of NiO. The oxide grain size and the thickness of the oxide layer all reduce with increasing of Hf content. The oxide scale of the alloy with different Hf content is made up of an outer NiO layer with a small amount of Co₃O₄, inner Al₂O₃ and Cr₂O₃ layer with a small amount of TaO₂.