| AVS 54th International Symposium | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | K. Kusaba, Tokai University, Japan |
| Authors: | H. Shindo, Tokai University, Japan T. Mitomi, Tokai University, Japan M. Suzuki, Tokai University, Japan K. Kusaba, Tokai University, Japan |
| Correspondent: | Click to Email |
A low temperature and low damage silicon oxidation technique is highly required in various ULSI processes. In particular for trench isolation of a memory cell to realize further integrations, the oxidation should be ion-assisted for directionality but with low damage. Additionally, a new type of MOS transistor with a trench gate has recently been proposed for the next generation of ULSI. For this purpose, a new method of negative ion assisted silicon oxidation has been proposed employing microwave oxygen plasmas. In this work, a new method of negative ion assisted silicon oxidation is proposed employing microwave oxygen plasma, and a directional and low temperature silicon trench oxidation will be demonstrated. The oxidation characteristics were intensively studied in silicon trench to form a shallow trench insulation layer for cell isolation of MOS transistor. The plasma was produced in an aluminum chamber 240 mm in diameter. At the one end of the chamber, a microwave of 2.45 GHz was introduced through a high permittivity material of AlN (permittivity: 10.9) window of disc plate. The oxidation characteristics were precisely examined in a silicon trench of 0.15 um width and 0.2 um depths. The oxidation was made in the condition of 400 degree C and the bias frequency of 1900 kHz. The oxidation depth at the three positions of the trench was determined from SEM photograph. These three positions are labeled as “Top, Side and Bottom” The oxidation depth at all positions was at first decreased with an increase in the axial distance from the microwave window, but it was increased again in the downstream. Particularly, the oxidation depth at the trench bottom showed a maximum in a very downstream of 18 cm from the window, and thus the step coverage of the trench oxidation, defined as the depth ratio of the trench bottom to the top, reached as high as 0.8. Since the axial distance at which the oxidation depth begins to increase again is just coincident with the region where the electron energy is rapidly decreased, this directional oxidation feature is ascribable to the negative oxygen ions. It is concluded that the oxidation by high density oxygen surface-wave plasma with high permittivity window is innovative.