Microwave breast imaging is a painless and nonradiation method. This pilot study aimed to evaluate the detective capability and feasibility of a prototype of a portable breast cancer detector using a radar-based imaging system. Five patients with histologically confirmed breast cancers with a minimum diameter of 1 cm were enrolled in this study. The antenna array dome of the device was placed on the breast of the patient in a supine position for 15 min per single examination. The primary endpoint was a detection rate of breast cancers. The secondary endpoints were positional accuracy and adverse event. All five targeted breast tumors were detected and were visualized at the sites confirmed by other diagnostic modalities. Among five tumors, one was not detected via mammography because of heterogeneously dense breast and another was a microinvasive carcinoma of invasive tumor size 0.5 mm. No study-related adverse events occurred. The prototype of a portable breast cancer detector has sufficient detective capability, is safe for clinical use, and might detect an early stage breast cancer, such as noninvasive carcinoma. Future developments should focus on further decreasing the size of the machine and shortening inspection time.
A novel scalable low dielectric constant (low-k) film technology was developed by use of self-assembled porous silica. Non-periodic disordered porous silica film structure was formed on a Si wafer by spin-coating a precursor solution with micelles of surfactant and a silica oligomer. Polyoxyethylene-polyoxypropylene-polyoxyethylene (EOPOEO) triblock copolymers and tetraethyl orthosilicate (TEOS) were used as a surfactant and a silica oligomer, respectively. A novel tetramethylcyclotetrasiloxyane (TMCTS) vapor treatment process was developed to reinforce mechanical properties of the porous silica film and to recover process-induced damages. New copper (Cu) electroplating solution and post cleaning process of chemical mechanical polishing (CMP) were developed to improve leakage current characteristics and dielectric constant of the porous silica low-k film. Cu/porous silica low-k damascene structures were fabricated and their characteristics were investigated.
We have developed sol-gel self-assembly techniques to control the pore structure and diameter of ultra-low-k interlayer dielectric (ILD) films. Porous silica films have been fabricated using cationic and nonionic surfactants as templates, resulting in 2D-hexagonal and disordered pore structures, respectively. The disordered mesoporous silica film has a worm-hole like network of pore channels having a uniform diameter. Precursors of the mesoporous silica films were synthesized by use of tetraethyl-orthosilicate (TEOS), inorganic acid, water, ethanol and various surfactants. The surfactants used were cationic alkyltrimethyl-ammonium (ATMA) chloride surfactants for 2D-hexagonal pores and nonionic tri-block copolymer for disordered structures. Dimethyldiethoxysilane (DMDEOS) was added for forming the disordered mesoporous silica. The disordered cylindrical pore structure with a uniform pore size was fabricated by controlling the static electrical interaction between the surfactant and the silica oligomer with methyl group of DMDEOS.
Tetramethylcycrotetrasiloxane (TMCTS) vapor treatment was developed, which improved the mechanical strength of mesoporous silica films. The TMCTS polymer covered the pore wall surface and cross-linked to passivate the mechanical defects in the silica wall. Significant enhancement of mechanical strength was demonstrated by TMCTS vapor treatment. The porous silica film modified with a catalyst and a plasma treatment achieved higher mechanical strength and lower dielectric constant than conventional porous silica films because the TMCTS vapor treatment was more effective for mechanical reinforcement and hydrophobicity.
In order to develop ultra-low-k interlayer dielectric films for ULSIs in 45 nm technology generation, a self-assembly technology was introduced to form porous silica films. The precursor solution for the self-assembly contained cationic surfactant such as alkyltrimethylammonium chloride (ATMACl) and TEOS in ethanol diluted with water. It was spin-coated on a Si wafer so that 2-dimentional hexagonal configuration of self-assembled cylindrical micelles was
formed on the wafer, resulting in formation of the 2-dimensional hexagonal structure of the cylindrical tubes of silica after calcination. The pore diameter and the resulting dielectric constant can be controlled by the number of carbon atoms in the alkyl chain of ATMACl surfactant. A nonionic surfactant such as polyethylene oxide (PEO)-polypropylene oxide (PPO)-PEO triblock copolymer was also used to form disordered porous silica as well as periodic porous silica
films. The mechanical properties of the self-assembled porous silica film were reinforced without changing the dielectric constant by introducing tetramethyl-cyclo-tetra-siloxane (TMCTS) treatment. Significant enhancement of elastic modulus (E) and hardness (H) was achieved by TMCTS treatment at 350°C. The effect of TMCTS treatment on the reinforcement of disordered porous silica was demonstrated. Another important property of porous low-k film is adhesion. TMCTS treatment increased the adhesion of the porous low-k silica film at the Si interface significantly. High modulus porous silica films were formed and E of 8 GPa and k of 2.07 were achieved simultaneously. Cu/low-k damascene structure for 45-nm BEOL technology was demonstrated successfully.
Characteristics of photosensitive low-k methylsilsesquioxane (MSQ) were investigated by use of electron-beam lithography. Photosensitive low-k MSQ makes it possible to realize via and trench patterns for Cu damascene technology in the ultra-large-scale-integrated (ULSI) circuit multilevel interconnect integration without dryetching processes. In this paper the dependences of exposure dose, humidification treatment and development method on critical dimension were investigated. It is found that longer humidification treatment resulted in the lower critical exposure dose, while the feature sizes were enlarged. The feature sizes had a linear correlation with exposure dose. Then reduction of the critical exposure dose minimizes the feature sizes. The development with ultrasonic wave was developed to reduce the critical exposure dose for 100 nm line and space pattern with the aspect ratio 3.3.
Aluminum-germanium-copper (Al-Ge-Cu) alloy is a promising material for interconnections to fill contact holes and vias using low temperature reflow sputtering due to its lower melting point than conventional Al alloys. The reflow temperature for contact- and via-filling decreases as the Ge concentration in Al increases. The suitable Ge concentration for reflow sputtering at around 400 degree(s)C is 1 wt.% of Ge. The electromigration characteristics for the Al-1%Ge-0.5%Cu alloy are investigated. It becomes clear that electromigration lifetime for Al-1%Ge-0.5%Cu is similar to that for Al-1%Si-0.5%Cu. The activation energy and n value are 0.56 eV and 3.4 for Al-1%Ge-0.5%Cu, and 0.64 eV and 4.7 for Al-1%Si-0.5%Cu. It is also found that intermetallic compounds of Al-Ti-Ge are formed at grain boundaries after reflowing.
Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.