This research investigates the gap-fill characteristics of Cu in back-end-of-line (BEOL) interconnects, focusing on Co liner deposition using chemical vapor deposition (CVD) and cyclic-CVD (C-CVD). Providing superior gap-fill characteristics for BEOL interconnect applications is important. Three methods-CVD, C-CVD, and a combination of the two-were compared in terms of their effects on Cu reflow and electrical performance. CVD exhibited the lowest resistivity (44 mu Omega cm at 10 nm thickness) and the fewest carbon impurities, confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Atomic force microscopy (AFM) revealed that CVD produced the smoothest surface (Rq similar to 0.5 nm), enabling better adhesion and uniform Cu reflow. At 300 degrees C, Co liners deposited by CVD achieved void-free Cu-Mn filling in 20 nm trenches, which showed CVD to outperform other methods. These findings highlight CVD as the most effective technique for precise Co liner deposition, ensuring reliable Cu interconnects in advanced semiconductor nodes.

Herein, TaN thin films were deposited using direct current (DC) magnetron sputtering enhanced by side magnets. The produced TaN films were optimized to be used as diffusion barriers for backend-of-line (BEOL) microelectronics. The side magnets were strategically placed to control magnetic field distribution, enabling precise tuning of the etch-to-deposition ratios and the Ta/TaN thickness profiles. TaN films were deposited on silicon substrates at N2 flow rates of 5-54 sccm, and they were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The optimized N2 flow rates were determined to be 10-18 sccm. These flow rates along with RF bias and magnetic field control improved the step coverage and densification for high-aspect-ratio trenches. XRD and XPS revealed a transition from metallic beta-Ta to cubic TaN, forming a nitrogen-rich phase with remarkable barrier properties. ToF-SIMS depth profiling indicated that the TaN layer suppressed Cu diffusion under thermal stress (345 degrees C; 5 min), confirming the robustness of the TaN layer in Cu-Mn/Co/Ta/TaN stacks. Integrating a side magnet with the sputtering system enhanced plasma confinement and film uniformity, thereby advancing the development of Ta/TaN deposition. These findings highlight the potential of magnetic field control in sputtering systems, offering valuable insights into diffusion-barrier technology for next-generation BEOL processes.

This study aims to demonstrate the deposition of high-performance Cu-seed layers using a very high frequency-direct current (VHF-DC) superimposed magnetron sputtering system for sub-20-nm dual-damascene interconnects. Plasma diagnostics revealed substantial improvements in plasma properties with electron densities measured at ne approximate to 1.71 x 1016m-3 for direct current magnetron sputtering (DCMS), ne approximate to 3.08 x 1016m-3 for 40.68 MHz VHF-DC, and ne approximate to 1.63 x 1017m-3 for 60 MHz VHF-DC. These enhancements enabled superior step coverage and thin-film uniformity, particularly in high-aspect-ratio structures, achieving a bottom-to-top coverage ratio exceeding 100 % at an RF bias of 200 W. Comparative analysis using X-ray diffraction and Xray photoelectron spectroscopy showed that Cu-Mn films deposited via VHF-DC superimposed sputtering exhibited improved Cu (111) crystallinity, reduced void formation, and enhanced adhesion compared to conventional DCMS. These findings reveal VHF-DC superimposed sputtering as a critical technological advancement, offering enhanced process reliability and scalability for next-generation semiconductor devices.

We will report our development results of phase-change and ferroelectric thin film processing technologies including sputtering, MOCVD and plasma etching as well as manufacturing processes for PCRAM, FRAM and MEMS/Sensor device applications. Thin-film functional material such as phase-change materials and ferroelectric materials have been utilized to form advanced semiconductor and electronic devices for internet of things (IoT) solutions. We are confident our manufacturing technologies for these materials and devices will contribute to realizing next generation Smart Society.

Cu interconnects are used in semiconductor devices and their dimensions are downscaled markedly. Cu interconnects are fabricated by a damascene process, and it becomes difficult to fill Cu into trenches and vias structures by electroplating below the 20 nm feature size. We evaluated the process integration for Cu interconnects using a Co wetting layer by chemical vapor deposition (CVD), a Cu seed by magnetic-field-assisted ionized sputtering (MFIS) and a Cu reflow technique. The properties of a CVD-Co film, such as composition, resistivity, step coverage, and adhesion between Cu and Co, were investigated. By using CVD-Co as the wetting layer, the properties of Cu gap filling in a trench structure were improved, and the filling of Cu into a 14-nm-wide trench structure was achieved.

TaOx thin films were fabricated by O2 reactive Radio Frequency (RF) magnetron sputtering on 8inch substrate using a Ta metal target at room temperature for mass-production of ReRAM. The TaOx thin films had good uniformity (±1%), excellent stability(±1%) at the sputtering process. Ta/TaOx(10nm)/Pt-ReRAM cell was confirmed the bipolar switching and excellent endurance property to 7×108 cycles with large on/off resistance ratio above 1,000 at high speed operation (50nsec, ±3V).

Fig.2. Cross section SEM image of GST filling profile prepared by a) conventional type sputtering and b) Long Throw Sputtering (LTS). Phase Change Random Access Memory (PCRAM) is one of the candidates for next generation memory due to its non-volatility, high speed, high density and compatibility with Si-based semiconductor process. Reduction of reset current is considered to pose a major technical challenge, a future memory device may need a new phase change material featuring a low melting point. Ge doped SbTe material (Ge:SbTe=SGT) has a melting point (540 ) of about 100 lower than that of Ge2Sb2Te5 (GST). [1] In the other hand, in order to integrate PCRAM to beyond 512Mbit, thermal interference between small memory cells become a problem. To resolve this problem, Confined Cell structure PRAM was suggested. [2] However, it was difficult to fill GST layer in a small hole with a conventional sputtering tool because a big overhang occurred. In this work, we prepared SGT films on the small hole patterned wafer by a new concept sputtering tool which designed developed a new concept sputtering tool. The structure of SGT film was observed with cross section SEM and the film composition was measured with XRF. It was observed an overhang was suppressed and a SGT film was filled in a small hole with a new concept tool. In addition, the uniformity of the SGT film composition was good at less than 3% in 200mm substrate. A multi-chamber sputtering system ULVAC ETRONTM-EX was used for SGT deposition on the small hole patterns substrates. SGT films were deposited at R.T. by magnetron sputtering with a 300mm sintered target. A scanning electron microscope (SEM) was used to observe the filling profile of SGT. The Sheet resistances of the SGT films are measured by Omnimap RS-100 (KLA tencore). The process flow of test device is shown in Figure 1. The fabricated device was reversibly switched between crystalline (set) and amorphous (reset) phases using a pulse generator. The voltage and the width of set and reset pulse were 500nsec and 100nsec respectively. Figure 2 shows cross section SEM images of SGT filling profile prepared by a) conventional type and b) LTS. An overhang was formed by the conventional type sputtering tool because the sputtering atoms were scattered. On the other hand the mean free path was long with low pressure in LTS tool [3]. The sputtering atoms reached to the bottom in a hole directly. Therefore an overhang was suppressed. Figure 3. shows the relation between the voltage of the reset pulse and an electric current of GST and SGT in a test device. The reset voltage of SGT was small compared with GST. The reset current of SGT was also lower than GST. It is considered as the small electric power with a reset step because the melting point of SGT is low. Reference [1] J.Jeong., et al, 2007 MRS Spring Meeting, I11.3. [2] S.L.Cho., et al, 2005 Symposium on VLSI Technology Digest of Technical Papers,6B-1. [3] N.Motegi, et al, Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 13(1995), pp. 1906-1909.

The reactive ion etching (RIE) of the binary transition-metal oxides (TMOs) NiO, CuO and CoO, which are expected to be key materials of resistance random access memory (RRAM (TM)), was investigated. We found that inductively coupled plasma using CHF(3)-based discharge, which is highly compatible with conventional semiconductor RIE, is effective for the TMOs studied here. Furthermore. device fabrication using Pt/CoO/Pt trilayers is carried out, and a large change in resistance, which is an essential functionality of RRAM, was successfully observed. This should be definite evidence of a successful RIE realized in the present device fabrication.

We have developed a Pb(Zr,Ti)O-3 (PZT) piezoelectric thin-film-actuator manufacturing technique by sputtering and dry etching processes. PZT etching rate and taper angle were investigated, and we obtained a very high etching rate (about 190 nm/min) and a high taper angle (62 degrees). (001)/(100)-oriented PZT thin films on a (111)Pt/Ti/SiO2/Si substrate (6 in.) were prepared by RF magnetron sputtering, and Pt on PZT were prepared by DC magnetron sputtering. Pt/PZT/Pt piezoelectric thin-film actuators were fabricated by dry etching using an inductively super magnetron (ISM) plasma source. The characteristics of the ISM plasma source are high-density plasma and low-pressure operation attributable to the effect of the permanent magnet. The electrical properties of a piezoelectric thin-film-actuator cell fabricated by dry etching were investigated. The remanent polarization (P-r value) of a piezoelectric thin-film actuator with 3-mu m-thick PZT film was 41 mu C/cm(2) at an applied voltage of 30 V, and remanent polarization characteristics without the dependence on element size (30-300 mu m diameter) were obtained. Moreover, the displacement of a PZT thin-film-actuator was measured by contact atomic force microscopy (C-AFM), and a displacement of 4 nm was obtained at 3 pm thickness of the PZT film, 30-mu m-diameter element size, and an applied electric field of 100 kV/cm. It was clarified that the fabrication of PZT piezoelectric thin-film-actuators by dry etching using an ISM plasma source is effective.

Ge 2 Sb 2 Te 5 (GST) thin films were prepared on the small hole patterned wafer by a new concept sputtering tool which designed developed to fill a hole. The structure of GST film was observed with cross section SEM and the film composition was measured with XRF. It was observed an overhang was suppressed and a GST film was filled in a small hole with a new concept tool. In addition, the uniformity of the GST film composition was good at almost 1% in 200mmf substrate.

We prepared oxygen-doped and nitrogen-doped Ge-Sb-Te system thin film by RF magnetron sputtering, and investigated its crystallinity and resistivity with several annealing temperature and oxygen and nitrogen doping content. The test phase change device was fabricated to confirm switching characteristics between crystalline (set) and amorphous (reset) phases. The resistance of nitrogen-doped GST changed gradually and oxygen-doped GST shows a rapid resistance change with annealing temperature, since nitrogen-doped GST fee phase was held to high temperature as compared with the phase transition from fee to hep in oxygen-doped GST.