Teruo Shibano

Sidewall deposition film in platinum etching with Ar/halogen mixed gas plasmas

Experimental studies of the deposition of films formed on the sidewalls of a photoresist pattern in the etching of platinum films with Ar and halogen mixed gas plasmas were performed. In platinum etching with Ar/halogen gas plasmas there is no enhancement of the etch rate by adding halogen gases, and deposition films are formed on the sidewall of a photoresist pattern. The thickness of the sidewall deposition film is minimized in etching with pure Ar plasma. The addition of halogens increases the thickness of the sidewall deposition film. These films were analyzed by x-ray photoelectron spectroscopy (XPS) to investigate their formation mechanism. Carbon was detected even in the deposition films formed during etching with gases that did not include carbon. From the results of XPS analysis it was found that the etching reaction products from the photoresist relate to the formation of these films, and that the reason for the increase in the film thickness is the increase in the etch rate of the photoresist b...

Etching yields of SiO2 by low energy CFx+ and F+ ions

Etching yields of SiO2 by mass‐separated F+, CF+, CF2+, CF3+, and Ar+ ions have been measured at low ion energies ranging from 80 to 350 eV. CF3+ and CF2+ ions have higher etching yields than CF+ and F+ ions. At low ion energies, SiO2 cannot be etched and some film deposition is observed on the SiO2 surface. For example, in the case of CF+ ions, SiO2 can be etched at ion energies above 200 eV. This film deposition is caused by reactions of CFx+ ions at the SiO2 surface, and neutrals coming from the ion source also have some effect on this deposition.

Cold and Low-Energy Ion Etching (COLLIE)

It is shown that a new cold and low-energy ion etching system (COLLIE) is effective as a dry etching technique for fabrication of VLSI devices. In the COLLIE system, plasma instabilities are suppressed by an MHD stable magnetic field consisting of a solenoid coil and multicusp magnets. The ion temperature, which is strongly related to plasma instabilities, is lowered below 2 eV in this system. Etched profiles show a strong anisotropic feature without applying any external electrical bias. As small angular distribution of incident ions to a sample is realized, the microloading effect is greatly improved.

Platinum etching in Ar/Cl2 plasmas with a photoresist mask

Experimental studies of the etching of platinum have been performed with a photoresist mask in Ar/Cl2 plasmas. The etch rate of platinum decreased with addition of Cl2, showing no enhancement of etching by Cl2 addition. Moreover, the etch rate of platinum was found to be independent of substrate temperature in pure Cl2 plasmas. These results indicated that the platinum etching with chlorine-containing plasmas is proceeded mainly by physical sputtering due to incident ions, not by chemical reactions that produce volatile etch products. Thus, in platinum etching with Ar/Cl2 plasmas, the redeposition of nonvolatile etch products was observed to occur on sidewalls of the photoresist mask and platinum pattern; in this situation the etched profiles of platinum were tapered outwardly, because the redeposited films acted as etching masks for platinum. The thickness of deposited films on sidewalls increased with increasing Cl2 concentration, but they were found to be removed by wet treatment with HCl solutions. It...

Platinum etching in Ar/O2 mixed gas plasma with a thin SiO2 etching mask

Experimental studies of the etching of platinum with a SiO2 etching mask in an Ar/O2 mixed gas plasma were performed. The etching selectivity of platinum to SiO2 increases with the addition of oxygen, and a high etching selectivity of more than 6 is obtained around an oxygen concentration of 10%. This high etching selectivity is caused by the difference in the adsorption of oxygen atoms between platinum and SiO2. In the etching of SiO2 by an Ar/O2 plasma, oxygen atoms are removed by sputtering by incident ions; however, these vacant sites of oxygen are filled immediately by the oxygen atoms incident from the plasma. The surface etching of SiO2 in an Ar/O2 plasma is disturbed by these replacements of the oxygen atoms. On a platinum surface incident oxygen atoms do not stay on the surface, therefore, disturbance of the etching by oxygen adsorption does not occur. This difference in the oxygen adsorption between platinum and SiO2 is confirmed by the x-ray photoelectron spectroscopy analysis of the etched sur...

Etching of (Ba,Sr)TiO3 film by chlorine plasma

Experimental studies of the etching of (Ba,Sr)TiO3 (BST) have been performed in Ar/halogen and Cl2 plasmas. In spite of the poor volatility of halogenated barium and strontium, some chemical enhancement of the etching reaction was observed in the etching of BST with halogen-containing plasmas. An investigation of the etching of BaOx, SrOx, TiOx, and BaxSryOz films with Cl2 plasma showed that the chemical enhancement in BST etching was related to the existence of titanium in BST films. The chemical reactivity of titanium with chlorine seemed to enhance the etching of BST. In the x-ray photoelectron spectroscopy analysis of the BST surfaces etched with Cl2 plasma, we found that barium- and strontium-rich surfaces were formed during the etching and that etching residues consisting of barium and strontium were observed after the BST films were etched off.

Integration of BST thin film for DRAM fabrication

Abstract A process technique to integrate the sputter-deposited BST thin film into the DRAM is discussed. With some reconsiderations concerning the grain structure of the BST, the care of the electrode edge, the thermal stability of the capacitor characteristic, the upper dielectric of the capacitor and so on, the BST was successfully integrated into a capacitor TEG structure on a 9Mbits scale. By using the newly developed integration technique, a 4MDRAM was fabricated, exhibiting the normal bit function with a wide margin. After this, improvements on the thermal stability are needed by developing a barrier layer under the bottom Pt electrode that is more heat-resistant than currently achieved.

Measurement of Atomic Incorporation Rates and Modeling of Surface Reactions in (Ba, Sr)TiO3 Films Prepared by a Liquid Source Chemical Vapor Deposition

Atomic incorporation rates in (Ba, Sr)TiO3 [BST] films prepared by a liquid source chemical vapor deposition (CVD) method were measured using an X-ray fluorescence (XRF) method for several source supply ratios with different substrate temperatures (Ts) of 420–520°C. The atomic incorporation rates of Ba, Sr, and Ti increased with increasing incident flux of each source material, and subsequently the values became saturated. The activation energies Ea for the incorporated reactions were estimated using the Arrhenius plots of the saturated values. The Ea values were almost the same for Ba, Sr, and Ti, and were about 1.5 eV. The values were almost independent of the source supply ratios. From these experiments, we assumed a CVD model, where the precursors were transported onto the film surface and adsorbed there with their own sticking coefficients. In the model, the sticking coefficients of the Ba and Sr precursors (βBa and βSr, respectively) were effected by the species of precursors adsorbed thereon. The values of βBa and βSr estimated from the experiments were about 1.0×10-4 on the surface adsorbing Ti precursors, while they were about 1.0×10-3 on the other surfaces, i.e., surfaces excluding those adsorbing Ti precursors. The atomic incorporation rates of Ba, Sr, and Ti were numerically simulated, and were in good agreement with the experimental results for several source supply ratios with different Ts values of 420–520°C.

Integration of BaxSr1-xTiO3 thin film for DRAM application

This paper presents a newly developed process technology to integrate the BaxSr1-xTiO3(BST) thin film prepared by an rf magnetron sputtering. Evaluations of the integrated BST capacitors on a test element group (TEG) structure revealed some of key issues for a successful integration. A two-step sputtering method comprising the first step to form a nucleation layer and the second step to form the main part of the BST film was found to be useful for preventing the dielectric properties of the integrated BST thin film from the degradation. A careful control of the shape of the lower structures such as the edge of the bottom electrode or the poly Si plug of the storage node turned to be indispensable to obtain the reliable capacitor and this recommends the extensive use of the process that can provide a flush surface such as the Chemical Mechanical Polishing (CMP) in the future integration. The interlevel dielectrics over the BST capacitor was shown to seriously affect the leakage characteristics and an undoped SiO2 film was most suitable for the integrity, implying the needs for another planarization technique instead of the glass reflow. Finally, a preliminary evaluation of the reliability and the normal bit function of a 4 Mbits DRAM, made of fully flat BST stacked capacitors, demonstrated the utility of the developed integration technology.