Ryoichi Mukai

High-aspect-ratio via-hole filling with aluminum melting by excimer laser irradiation for multilevel interconnection

This letter presents a technique for filling via holes on integrated circuits. The filling is achieved by momentarily melting an aluminum film with an optical pulse from an ArF excimer laser. This technique has been shown to allow excellent via filling without damaging lower levels of interconnect, and is applicable to filling submicrometer-diameter vias having a diameter of 0.6 µm with 0.7 µm depth (aspect ratio ∼1.2). The resulting surface was found to be planarized.

Signal-to-media-noise ratio improvement of CoCrPt-SiO2 granular perpendicular media by stacked Ru underlayer

In this work we have developed a stacked Ru underlayer and have studied its effects on the improvement of recording performances for CoCrPt-SiO2 granular-type dual-layer perpendicular media. The c-axis distribution ΔΘ50 of the 13.2 nm thick stacked Ru underlayer was 4.5°, which was about 33% smaller than that of Ru monounderlayer with the same thickness. The use of stacked Ru underlayer realized that the recording layer of granular-type media consisted of segregated fine-grain structure with oxide grain boundaries. The signal-to-media-noise ratio (SNR) improvement achieved by the use of the stacked Ru underlayer was indicated when it was compared with the use of Ru monounderlayers. Furthermore, the SNR for monopole head of 8.5 dB at 480 kfci and D50 of 356 kfci were obtained by optimizing the structure of stacked Ru underlayer.

Microstructure improvement of thin Ru underlayer for CoCrPt-SiO/sub 2/ granular perpendicular media

The microstructure improvement of the thin Ru layer was discussed in order to achieve excellent recording performance of the granular-type perpendicular media. The recording layers of granular-type media were deposited on different Ru underlayers by rf magnetron sputtering method with a composite-type sputtering target that consists of CoCrPt and SiO/sub 2/. The effects on the improvement of recording performances was analyzed. It was observed that the recording dependences of signal output and media noise are quite different but they show the same recording density dependences of signal-noise ratio (SNR). Realization of thin Ru underlayer for formation of high performance recording layer resulted in the investigation.

Single crystalline Si islands on an amorphous insulating layer recrystallized by an indirect laser heating technique for three‐dimensional integrated circuits

A new laser recrystallizing technique for producing single crystalline Si islands on an amorphous insulating layer has been developed. Si islands are recrystallized by indirect Ar ion laser heating utilizing a Si cap. This technique is an effective recrystallizing method for fabricating three‐dimensional integrated circuits. During recrystallization, this technique easily and stably produces a desired temperature profile to eliminate grain boundaries in recrystallized Si islands; the interior of the Si islands is kept cooler than the periphery and crystal growth begins from the interior. This desired temperature profile is realized because an Ar ion laser power is absorbed in the Si cap and heat flow takes place to the Si islands laterally as well as vertically from the heated Si cap through a separation cap. Damage to the underlying layer is not observed, which suggests that the laser beam power is cut in the Si cap. No grain boundaries are observed in more than 90% of the Si islands recrystallized with ...

Melt‐width enhancement in the recrystallization of polycrystalline silicon‐on‐insulator by twin‐laser‐beam‐induced substrate interheating

A new method to recrystallize polycrystalline silicon on amorphous insulating layers is developed using twin cw argon laser beams. It is found that the melt width of twin beams can exceed that of a single beam by a factor of 4. This effect is explained by a model of substrate interheating between twin laser spots. Using this technique, a large silicon single crystalline grain as large as 1.8 mm long and 20 μm wide was obtained on thermal oxide coated silicon wafers even for the substrate kept at room temperature during laser irradiation.

Interconnects on integrated circuits improved by excimer laser planarization for multilevel metallization

The use of excimer-laser planarization to improve interconnection on integrated circuits is described, and the effect of a thin Cu overcoating at the planarization step is considered. In the present experiment, the via-hole filling was achieved by melting an Al film with a single optical pulse (15 ns, approximately 5- approximately 20 J/cm/sup 2/) from an ArF excimer laser. This technique has been shown to realize excellent via filling without damaging the lower levels of interconnect, and is applicable to filling a via having a diameter of 0.7- mu m with approximately 1.0- mu m depth (aspect ratio approximately 1.4). The resulting surface was found to be planarized. The use of a thin Cu overcoating greatly enhances the Al planarization process by increasing the initial absorbance of the laser beam in the metal film, because the reflectivity of Cu ( approximately 20%) is lower than that of Al (>90%) for the ArF excimer laser beam.<<ETX>>

Monolayer of physically separated FePt islands with a tetragonal L1/sub 0/ structure produced by thermally created mass transport

A monolayer of physically separated FePt islands has been produced by thermally created mass transport of ultrathin FePt film, whereby formation of a magnetic layer composed of a two-dimensional arrangement of physically separated magnetic grains for decrease of magnetic coupling between the grains can be realized. The monolayer with [001] orientation was produced on [100] oriented MgO film. The produced monolayer had a small and uniform grain size and tetragonal L1/sub 0/ structure. Formation of granular film composed of a three-dimensional arrangement of L1/sub 0/-FePt ordered grains with [001] orientation in MgO film has been achieved by stacking the monolayer of FePt islands with MgO separation layers for high-density perpendicular media.

3-Dimensional SOI/CMOS IC's fabricated by beam recrystallization

A 3-Dimensional (3-D) CMOS integration with a structure, in which one type of transistor is fabricated directly above a transistor of the opposite type with separate gates and an insulator in between, has successfully been fabricated by using laser beam recrystallization. Seven-stage ring oscillators fabricated in the 3-D structure have a propagation delay of 430psec per stage at a supply voltage of 5V, which is comparable to that of single-crystal Si devices. This CMOS structure and the process technologies we have developed in this work can be the basis for realizing a multi-layered 3-D integration composed of vertically stacked transistors with separate gates and an insulating layer in between.

Magnetic coupling between grains in CoCrPt/Cr thin film improved by decrease of the deposition temperature and post-annealing

A technology for decreasing the magnetic coupling between grains in CoCrPt/Cr thin-film system has been investigated, whereby a formation technology for a magnetic thin film is developed for high-performance longitudinal recording media. An increase of coercivity and the decrease of magnetic coupling between grains can be achieved. Since the decrease of magnetic coupling between grains results in an increase of coercivity and a decrease of media noise, the value of Hc/Hkgrain must increase to the maximum value of 0.5 in the case of media produced on a nontextured disk. The increase of Hc/Hkgrain can be realized by segregating nonmagnetic elements at the grain boundaries of a Co-based alloy. The effect of post-annealing on the segregation has been investigated. In the Co-based alloy/Cr structure case, Cr as nonmagnetic element is diffused from the Cr underlayer into the Co-based alloy magnetic layer during this post-annealing, resulting in segregation at the grain boundaries. It has been found that the rem...

Metal plugs produced by excimer laser melting for submicron interconnection: mechanism, electrical properties

A new laser planarization technique for producing metal plugs has been developed. In this technique, a thin metal cap which is patterned to cover the entire via hole is used, followed by melting with a XeCl excimer laser irradiation. The molten metal cap is drawn into the via by surface tension forces resulting in the formation of the metal plug. The use of the metal cap means that the plug formation is performed easily and stably. And is an effective method for submicron interconnection. The interconnects were tested on a contact check device composed of 60000 vias connected in series. The characteristics agree well with the results calculated using the electrical resistivity of metal.<<ETX>>