Gap-filling Process Research Articles

Low-Shrinkage Spin-On Glass for Low Parasitic Capacitance Gap-Filling Process in Advanced Memory Devices

A new low-dielectric-constant spin-on glass (SOG) with a k value of 2.4 has been developed for a gap-filling process in advanced memory devices. The low-shrinkage characteristic of the SOG during thermal curing provides capabilities of gap filling and planarizing as high as those of conventional reflowable SOGs. The low-shrinkage SOG has thermal stability up to 800 °C and chemical stability against diluted hydrofluoric acid, sulfuric acid–hydrogen peroxide, and amine-based solutions, which makes it possible to be used as an interlevel dielectric of memory devices. Tungsten and aluminum interconnects fabricated using the low-shrinkage SOG showed a parasitic capacitance 30% lower than those fabricated using silicon dioxide and a sufficiently long line-to-line dielectric breakdown lifetime. Taking advantage of the high chemical stability of the SOG, an all-wet damageless via-formation process using an amine-based photoresist stripper has been developed. By using the process, the low-shrinkage SOG can be applied to multilevel metallization.

Issues and Challenges for a Modern English-Arabic Dictionary

Lexicography in the Arab world has had important effects on the development of the Arabic language. The origin and subsequent development and refinement of traditional Arabic grammatical theory—as early as the eighth century- had intimate links with the practice of writing dictionaries. The Kitab al-ʿayn , by al-Khalil ibn Ahmad (d.c.786), which is the first full-scale dictionary in the Arab world, marked a significant milestone in the history of grammatical thought and set the tone for more works on Arabic grammar. For many centuries, the general mode of the theory has acknowledged a "closed" corpus of Qur'anic diction and pre-Islamic poetry and prose as the major source of Arabic lexicographic works. The main credo is that Arabic dictionaries should contain the "unattained" forms of the language and remain impervious to external persuasions; namely colloquialisms, borrowings, neologisms, and coinages. Arabic dictionaries continued to resist the slightest reform as to the codification of lexical innovations and the treatment of lexical gaps exhausting themselves to the point of stagnation. Today, English-Arabic dictionary editors have to deal with a huge number of lexical gaps that have cumulated over time. The lexical gap-filling process is carried out in a very unsystematic way that is far from creating an atmosphere of cooperation that ultimately contributes to creating unified English-Arabic lexical databases for lexicographic purposes. The paper explains how a modern English-Arabic dictionary can fall short in its modernizing role, and gives a snapshot of the most salient microstructural issues that characterize the Al-Mawrid Al-Hadeeth: A Modern English-Arabic Dictionary (2010).

Misalignment Study by Etch Induced Silicon Damage in Single Crystal Etch Process for Shallow Trench Isolation Structure

We studied the misalignment between active and gate layer in terms of silicon dislocation caused by high temperature anneal process in SOG based STI gap-fill process. The SOG process is one of good candidates to overcome gap-fill limitation due to its excellent gap-fill characteristics. However, the SOG process needs high temperature anneal process to convert from Si-H, N-H to Si-O bond, which leads to the misalignment due to large stress change. We suggest that silicon defect is generated from ion bombardment at trench etch process and accelerated from hysteresis at anneal process. The O2 cure process is known as one of feasible methods to cure silicon damage through recrystallization. Based on this model, the misalignment was significantly improved as removing the defect through O2 cure process following trench etch process.

GOI Improvement in 65nm Sacrificial Oxide Free Process Integration

GOI (Gate Oxide Integrity) improvement in 65nm SAC OX (Sacrificial Oxide) free process integration was studied in this paper. After studying the effects of various processes in STI (Shallow Trench Isolation) module with SAC OX free scheme on GOI, it was found that the dominant process that could degrade GOI was the STI HDP (High Density Plasma) gap fill process. STI HDP gap fill process could cause Si damage on AA corners, also named as AA clipping, which will result in irregular corners and hence a thinner gate oxide formation at imperfect AA corners. This was observed by a TEM (transmission electron microscopy) study. In SAC OX free scheme, the exposed AA Si corners that were damaged during the HDP process did not get consumed and repaired while they would have gotten in the scheme with SAC OX and hence degraded GOI. By optimizing the STI gap fill processes and hardware configuration, the AA clipping can be greatly reduced and GOI can be improved to the required level.

Advanced HDP STI Gap-Fill Development in 65nm Logic Device

High density plasma chemical vapor deposition (HDP-CVD) has been proven to be a sucessful process for shallow trench isolation (STI) gap fill in advanced CMOS device fabrication. As CMOS technology nodes continue to shrink, STI gap-fill requirement become more and more challenging. To keep pace with the stringent requirements, a novel HDP gap-fill process - Integrated Proess Modulation (IPM) has been developed to fill these aggressive structures. IPM process, which is extending from Deposition - Etch - Deposition (DED) process, is made of a serial of deposition/etch cycles, which is one of techniques to keep trench open by using NF3-based plasma dry etch before the trench nearly closed by film deposition. Based on this process model, HDP gap-fill capability has been greatly extended to 65nm and beyond. This paper summarizes the STI gap-fill development and optimization work of IPM processes

Lewis-base copper(I) formates: Synthesis, reaction chemistry, structural characterization and their use as spin-coating precursors for copper deposition

Consecutive synthesis methodologies for the preparation of a series of copper(I) formates [L m CuO 2CH] (L = n Bu 3P: 4a, m = 1; 4b, m = 2; 5, L = [Ti](C CSiMe 3) 2, m = 1, [Ti] = ( η 5-C 5H 4SiMe 3) 2Ti) and [L m CuO 2CH·HO 2CR] (L = n Bu 3P: 7a, m = 1, R = H; 7b, m = 2, R = H; 7c, m = 2, R = Me; 7d, m = 2, R = CF 3; 7e, m = 2, R = Ph. L = ( c C 6H 11) 3P, R = H: 8a, m = 2; 8b, m = 3. L = (CF 3CH 2O) 3P, R = H: 9a, m = 2; 9b, m = 3. L = (CH 3CH 2O) 3P, R = H: 10a, m = 2; 10b, m = 3. L = [Ti](C CSiMe 3) 2; m = 1: 11a, R = H; 11b, R = Ph) is reported using [CuO 2CH] ( 1) and L ( 2a, L = n Bu 3P; 2b, L ( c C 6H 11) 3P; 2c, L = (CF 3CH 2O) 3P; 2d, L = (CH 3CH 2O) 3P; 3, L = [Ti](C CSiMe 3) 2) as key starting materials. Addition of formic acid ( 6a) or carboxylic acid HO 2CR ( 6b, R = Me; 6c, R = CF 3; 6d, R = Ph) to the afore itemized copper(I) formates 4 and 5 gave metal–organic or organometallic 7– 11. The molecular structures of 8a and 11a in the solid state are reported showing a threefold coordinated copper(I) ion, setup by either two coordinatively-bonded phosphorus atoms and one formate oxygen atom ( 8a) or two π-bonded alkyne ligands and one oxygen atom ( 11a). A formic acid molecule is additionally hydrogen-bonded to the CuO 2CH moiety. The use of 7b as suitable precursor for the deposition of copper onto TiN-coated oxidized silicon wafers by the spin-coating process below 300 °C is described. Complex 7b offers an appropriate transformation behavior into metal phase by an elimination–decarboxylation mechanism. The morphology of the copper films strongly depends on the annealing conditions. A closed grain network densified by a post-treatment is obtained (8 °C min −1, N 2/H 2 carrier gas). Hydrogen post-anneal to 420 °C after film deposition gave a copper film showing resistivities from 2.5 to 3.7 μΩ cm. This precursor was also used for gap-filling processes.

Use of landsat ETM+ SLC-off segment-based gap-filled imagery for crop type mapping

Failure of the Scan Line Corrector (SLC) on the Landsat ETM+ sensor has had a major impact on many applications that rely on continuous medium resolution imagery to meet their objectives. The United States Department of Agriculture (USDA) Cropland Data Layer (CDL) program uses Landsat imagery as the primary source of data to produce crop-specific maps for 20 states in the USA. A new method has been developed to fill the image gaps resulting from the SLC failure to support the needs of Landsat users who require coincident spectral data, such as for crop type mapping and monitoring. We tested the new gap-filled method for a CDL crop type mapping project in eastern Nebraska. Scan line gaps were simulated on two Landsat 5 images (spring and late summer 2003) and then gap-filled using landscape boundary models, or segment models, that were derived from 1992 and 2002 Landsat images (used in the gap-fill process). Various date combinations of original and gap-filled images were used to derive crop maps using a supervised classification process. Overall kappa values were slightly higher for crop maps derived from SLC-off gap-filled images compared to crop maps derived from the original imagery (0.3–1.3% higher). Although the age of the segment model used to derive the SLC-off gap-filled product did not negatively impact the overall agreement, differences in individual cover type agreement did increase (−0.8%–1.6% using the 2002 segment model to −5.0–5.1% using the 1992 segment model). Classification agreement also decreased for most of the classes as the size of the segment used in the gap-fill process increased.

Treefall-gap structure and regeneration in mixed Abies alba stands in central Poland

This study investigates the roles of treefall-gaps in tree regeneration processes and the development of stand structure in a series of stands in which silver fir ( Abies alba Mill.) co-occurs with other conifers and numerous angiosperm trees in central Poland. The study was conducted in the Jata Reserve, near the north-eastern limit of this silviculturally important tree species. Sixty-eight treefall-gaps (minimum canopy opening of 20 m 2) were objectively located along transects, sampled for gap characteristics and tree regeneration patterns, and compared to comparable sites from beneath closed canopies. Gap size did not influence the quantity of seedlings and saplings of different tree species. Numbers of seedlings and saplings in gaps were related to species composition of the surrounding tree canopy, especially the abundance of fir. The main potential successors in gaps were hornbeam (29% of the total), sycamore (20%) and fir (19%). Based on the current stand structure and gap-filling processes, silver fir is likely to remain present in the canopy but the relative proportion of the canopy composed of hornbeam will increase substantially. These results help to clarify the role of treefall disturbances in the dynamics of mixed stands near the north-eastern limit of silver fir, and, consequently can inform the evaluation of silvicultural practices.

Hydrogen Ion Drift into Underlying Oxides by RF Bias during High-Density Plasma Chemical Vapor Deposition

High-density plasma chemical vapor deposition (HDP-CVD) is a deposition method of current interest for the gap-filling process of the intermetal dielectric (IMD) in semiconductor circuits. We first demonstrated that hydrogen ions drift into underlying thermal oxides during HDP-CVD with a SiH4–O2–Ar system, and that they degrade the reliability of gate oxides. The characteristics of the oxides were investigated using secondary ion mass spectroscopy (SIMS), thermal desorption spectroscopy (TDS), and capacitance–voltage (C–V) measurements of metal–oxide–semiconductor (MOS) capacitors. The hydrogen ions that are dissociated from SiH4 in plasma penetrate into the HDP-CVD oxides, and some of the hydrogen ions in the HDP-CVD oxides drift into the underlying thermal oxides by rf bias. The drifting hydrogen creates two chemical bonding states and generates hole trap sites in the underlying thermal oxides.

Gap-Fill Process of Shallow Trench Isolation for 0.13 µm Technologies

Gap-fill technology using high-density plasma chemical vapor deposition (HDP-CVD) is one of the leading technologies in 0.13 µm generation semiconductor device processing. The analysis of the dependence of HDP-CVD filling characteristics on the processes used revealed that film deposition under an increased plasma power and low-pressure conditions is effective for stable gap filling. By optimizing these process parameters, we were able to implement shallow trench isolation (STI) of space width 0.13 µm and aspect ratio 3.9. Furthermore, we demonstrated that the angular dependence of sputter yield and the ionic deposition mechanism are important factors when performing filling by means of HDP-CVD. The filling characteristics can be improved by increasing the maximum sputter yield angle and the amount of ionic deposition component. Based on these mechanisms, we constructed a topography simulation model which enables accurate expression of the topography of the HDP-CVD film.

Calibration Method for High-Density-Plasma Chemical Vapor Deposition Simulation

We present a consistent calibration method for high-density-plasma chemical vapor deposition (HDP-CVD) topography simulation using the gap-filling process of the inter-metal dielectric (IMD). For the HDP-CVD model, four phenomena, thermal deposition, ion-enhanced deposition, sputter-etching by Ar+ ion, and redeposition, were considered. The contribution of each phenomenon to surface evolution was determined on the basis of six parameters. All six parameters were calibrated by methods including deposition/etching rate measurement, an experiment using the test structure and plasma simulation. The simulation calibrated by these methods has high predictive accuracy in terms of the gap-fill capability in trenches.

A shallow trench isolation using nitric oxide (NO)-annealed wall oxide to suppress inverse narrow width effect

A simple method to suppress INWE of transistor based on STI technology has been demonstrated in this paper. In order to prevent the boron out-diffusion through the trench sidewall, the nitric oxide (NO)-annealed wall oxidation is performed before the gap-filling process. By reviewing the electrical properties of n- and p-MOSTs, it has been confirmed that INWE of n-MOST can be easily suppressed without any problem in p-MOST, and the uniformity of parameter can be remarkably improved by this method. Also, the gate oxide integrity and the junction leakage current have been evaluated in the device reliability point of view, and it is confirmed that there are no problems to use this technique in STI technology.

Random PCR-based genome sequencing: a non-divide-and-conquer strategy.

We propose a genome sequencing strategy, which is neither divide-and-conquer (clone by clone) nor the shotgun approach. Random PCR-based and PCR relay sequencing constitute the basis of this novel strategy. Most of the genome is sequenced by the former process that requires only a set of non-specific primers and a template DNA. Random PCR-based sequencing reduces redundancy in sequencing by exploiting known sequence information. The number of primers required for random PCR was significantly diminished by using a combination of primers. The former process can be partially replaced by the shotgun method, if necessary. The gap-filling process can be effectively performed by way of PCR relay. The feasibility of this strategy was demonstrated using the Escherichia coli genome. This strategy enhances the global effort towards genome sequencing by being available through the Internet and by allowing the use of preexisting sequence data.

Advanced planarized passivation for sub-micron technology

An advanced passivation gap-fill process was developed for sub-micron technology. Excellent gap-fill was achieved using the stack of triethoxyfluorosilane (TEFS) doped fluoro-silicate (FSG) and silicon nitride films. This TEFS-based gap-fill process provides both high throughput and cost-effective planarized passivation. The TEFS-FSG film can completely fill 0.45 μm width ×0.9 μm height gap. No forbidden void or cavity was observed in larger gaps wider than 1 μm after the deposition of a silicon nitride cap-layer. Various reliability tests such as pressure cooker test, corrosion test, and seven-alloy anneal test were carried out. Corrosion test result showed that there was no peeling or corrosion mark on TEFS-FSG film deposited on TiN/Ti/Al metal wafers. FTIR data indicated there was no water absorption in TEFS-FSG film after pressure cooker and corrosion tests.

Air-gap formation during IMD deposition to lower interconnect capacitance

The use of air-gaps between interconnect metal lines to reduce interconnect capacitance has been explored. Simulations were performed to determine the reduction in capacitance obtainable using air-gaps. The formation of air-gaps in the isolation oxide between metal lines was simulated using Stanford Profile Emulator for Etching and Deposition in IC Engineering (SPEEDIE). The capacitance of the SPEEDIE profiles was then extracted using Raphael (an electrical analysis simulator from TMA). The feasibility of air-gaps was also demonstrated experimentally. Fabricated air-gap structures exhibited a 40% reduction in capacitance when compared to a HDP-CVD oxide gap-fill process with K=4.1. Additionally, the air-gap structures did not exhibit any appreciable leakage current.

Second pathway for completion of human DNA base excision-repair: reconstitution with purified proteins and requirement for DNase IV (FEN1).

Two forms of DNA base excision-repair (BER) have been observed: a 'short-patch' BER pathway involving replacement of one nucleotide and a 'long-patch' BER pathway with gap-filling of several nucleotides. The latter mode of repair has been investigated using human cell-free extracts or purified proteins. Correction of a regular abasic site in DNA mainly involves incorporation of a single nucleotide, whereas repair patches of two to six nucleotides in length were found after repair of a reduced or oxidized abasic site. Human AP endonuclease, DNA polymerase beta and a DNA ligase (either III or I) were sufficient for the repair of a regular AP site. In contrast, the structure-specific nuclease DNase IV (FEN1) was essential for repair of a reduced AP site, which occurred through the long-patch BER pathway. DNase IV was required for cleavage of a reaction intermediate generated by template strand displacement during gap-filling. XPG, a related nuclease, could not substitute for DNase IV. The long-patch BER pathway was largely dependent on DNA polymerase beta in cell extracts, but the reaction could be reconstituted with either DNA polymerase beta or delta. Efficient repair of gamma-ray-induced oxidized AP sites in plasmid DNA also required DNase IV. PCNA could promote the Pol beta-dependent long-patch pathway by stimulation of DNase IV.

Geometrical optimization of multilevel interconnects using Cu and low- k dielectrics

A comparison of propagation time and cross-talk for different technology variations was carried out. The calculation of parasitics was based on electrostatic field simulation in two dimensions, which also allows bounds to be obtained for three-dimensional effects such as line crossings in upper levels. The dependence of IC performance on the materials used for metallization was modelled. The simulation results recommend the use of copper and low- k dielectrics as a desirable alternative for aluminum and SiO 2. In addition to material substitutions, the circuit performance can be improved further by the optimization of the geometrical interconnection parameters such as the interconnect aspect ratio and the interlevel distance for the most critical interconnects. This is demonstrated for an advanced metalization scheme produced by a gap-fill process using encapsulated copper and low- k dielectrics.

Surface Related Phenomena in Integrated PECVD/Ozone‐TEOS SACVD Processes for Sub‐Half Micron Gap Fill: Electrostatic Effects

Surface related phenomena of subatmospheric chemical vapor deposition (SACVD) films were systematically studied on different types of plasma enhanced CVD (PECVD) oxides. The PECVD oxides are part of a new and in situ2 step gap fill process consisting of a thin PECVD underlayer and a thick SACVD oxide being proposed for advanced ULSI devices. Differences in deposition rates, wet etch rate, surface morphology, and stress‐temperature behavior of SACVD films deposited on PECVD oxide underlayers and bare silicon substrates were evaluated. For the PECVD underlayers which render surface dependence for the SACVD film, various plasma treatments of the underlayer was used to eliminate the effect. An extensive analysis of the surface and bulk properties of these PECVD oxide underlayers suggests that the occurrence of the surface dependence effects can be attributed to the presence of electronegative species such as fluorine on the surface of the PECVD oxide underlayer.

Lexical projection and the interaction of syntax and semantics in parsing.

A series of self-paced reading studies utilized an embedded anomaly technique to investigate long-distance dependencies with dative verbs. Previous research in our lab demonstrated that argument structure influences the gap-filling process. Experiment 1 extended that work by demonstrating that dative verbs pattern with other complex transitive verbs (i.e., a fronted filler that is implausible as the direct object will not be interpreted as the direct object until the absence of a noun phrase after the verb forces the postulation of a direct object gap. This pattern contrasts with that of transitive verbs that subcategorize for a single internal argument position, where fronted fillers are obligatorily interpreted as the direct object). Experiments 2 and 3 investigate the prediction that semantic analyses precede syntactic analyses in dative questions. It is argued that the lexical information about argument structure and thematic roles can guide semantic interpretation.

RecF-dependent and recF recB-independent DNA gap-filling repair processes transfer dimer-containing parental strands to daughter strands in Escherichia coli K-12 uvrB.

The processes for repairing DNA daughter-strand gaps were studied in UV-irradiated uvrB, uvrB recB, uvrB recF, and uvrB recB recF cells of Escherichia coli K-12. The dimer-containing parental DNA was found to be joined to daughter strands during postreplication repair in all four strains examined. Therefore, both the major (recF-dependent) and the minor (recF recB-independent) gap-filling processes repair DNA daughter-strand gaps by transferring parental strands into daughter strands.