• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.2
• /
• pp.93-98
• /
• 2001

YMnO$_3$ films are excellent gate dielectric materials of ferroelectric random access memories (FRAMs) with MFSFET (metal -ferroelectric-semiconductor field effect transistor) structure because YMnO$_3$ films can be deposited directly on Si substrate and have a relatively low permittivity. Although the patterning of YMnO$_3$ thin films is the requisite for the fabrication of FRAMs, the etch mechanism of YMnO$_3$ thin films has not been reported. In this study, YMnO$_3$thin films were etched with Cl$_2$/Ar gas chemistries in inductively coupled plasma (ICP). The maximum etch rate of YMnO$_3$ film is 285$\AA$/min under Cl$_2$/(Cl$_2$+Ar) of 1.0, RF power of 600 W, dc-bias voltage of -200V, chamber pressure of 15 mTorr and substrate temperature of $25^{\circ}C$. The selectivities of YMnO$_3$ over CeO$_2$ and $Y_2$O$_3$ are 2.85, 1.72, respectively. The selectivities of YMnO$_3$ over PR and Pt are quite low. Chemical reaction in surface of the etched YMnO$_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS) surface of the selected YMnO$_3$ thin films was investigated with X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry (SIMS). The etch profile was also investigated by scaning electron microscopy(SEM)

• Journal of the Microelectronics and Packaging Society
• /
• v.8 no.3
• /
• pp.49-53
• /
• 2001

Vortical etching experiments of ($SrBi_2Ta_2O_9$)/Si thin films have been performed by using the inductively coupled plasma reactive ion etching (ICP-ME) apparatus. The purposes of these experiments are to get the effective area of vertical surface. Because this technology is very important to get good qualities of ferroelectric gate structure, capacitor and the minimum parasitic effects related to the excellent performances of the FRAM (Ferroelectric Random Access Memory) device. The reacting gases were Ar and $Cl_2$gases, and various $Ar/C1_2$flow ratios were used. The etching experiments were carried out at various RF powers such as 700, 700, 500W and at various DC powers such as 200, 150, 100, 50W, respectively. The maximum etch rate of $SrBi_2Ta_2O_9$/Si thin films was 1050 A/min at the $Ar/C1_2$ gas ratio of 20/16, RF power of 700 W and DC power of 200 W. From the SEM (scanning electron microscopy) image of the SBT thin films, the wall angle was as good as about $82^{\circ}$.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.2
• /
• pp.49-54
• /
• 2003

We have investigated the effects of hydrogen annealing on the physical and electrical properties of $SrBi_{2}Ta_{2}O_9(SBT)$ thin films in the Pt/SBT/Si (MFS) structure and Pt/SBT/Pt (MFM) one, respectively. The microstructure and electrical characteristics of the SBT films were deteriorated after hydrogen annealing due to the damage of the SBT films during the annealing process. To investigate the reason of the degradation of the SBT films in this work, in particular, the effect of the Pt top electrodes, SBT thin films deposited on Si, Pt, respectively, were annealed with the same process conditions. From the XRD, XPS, P-V, and C-V data, it was seen that the SBT itself was degraded after $H_2$ annealing even without the Pt top electrodes. In addition, the degradation of the SBT films after $H_2$ annealing was accelerated by the catalytic reaction of the Pt top electrodes which is so-called hydrogen degradation. To prevent this phenomenon, we proposed the alternative top electrode material, i.e. Ir, and the electrical properties of the SBT thin films were examined in the $Ir/IrO_2/SBT/IrO_2$ structures before and after the H$_2$ annealing and recovery heat-treatment processes. From the results of the P-V measurement, it could be concluded that Ir is one of the promising candidate as the electrode material for degradation resistance in the MFM structure using SBT thin films.

• Journal of the Korean Vacuum Society
• /
• v.9 no.4
• /
• pp.315-320
• /
• 2000

We have investigated the crystal structure and electrical properties of Pt/SBT/$ZrO_2$/Si (MFIS) and Pt/SBT/Si (MFS) structures for the gate oxide of ferroelectric memory. XRD spectra and SEM showed that the SBT film of SBT/$ZrO_2$/Si structure had larger grain than that of SBT/Si structure. $ZrO_2$ film between SBT film and Si substrate is confirmed as a good candidate for a diffusion barrier by the analysis of AES. The remanent polarization decreased and coercive voltage increased in Pt/SBT/$ZrO_2$/Pt/$SiO_2$/Si structure. This effect may increase memory window of MFIS structure directly related to the coercive voltage. From the capacitance-volt-age characteristics, the memory windows of Pt/SBT (210 nm)/$ZrO_2$ (28 nm)/Si structure were in the range of 1~l.5 V at the applied voltage of 4~6 V. The current densities of Pt/SBT/ZrO$_2$/Si with as -deposited Pt electrode and annealed at $800^{\circ}C$ in $O_2$ambient were $8\times10^{-8} A/\textrm{cm}^2$ and $4\times10^{-8}A/\textrm{cm}^2$ , respectively.