| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+EM+MI+MS-TuM |
| Session: | ALD for Alternative Devices |
| Presenter: | Masafumi Kitano, Stanford University |
| Authors: | M. Kitano, Stanford University M. Nagase, Fujikin Incorporated, Japan N. Ikeda, Fujikin Incorporated, Japan P.C. McIntyre, Stanford University |
| Correspondent: | Click to Email |
Atomic layer deposition (ALD) has been widely discussed in the literature from various points of view. Typically, the amount of the precursor and reactant supplied into the ALD chamber is dictated only by controlling valve operation time, and is not quantitatively defined. To achieve a more quantitative ALD process, we have developed new flow rate control system (FCS) which can accurately dose precursor and reactant into an ALD reactor. This FCS consists of an orifice plate, pressure sensor, thermal sensor, and piezo control valve. It can be heated to 250˚C to achieve sufficient vapor pressure for most precursors used in ALD of various inorganic compounds and elements. The FCS controls the flow rate under critical expansion conditions (or choked flow conditions); the flow rate through the orifice is proportional only to the upstream pressure of the orifice.[1,2] The piezo control valve accurately controls the upstream pressure and, thus, the flow rate. This mode of operation makes it possible to control the dosing of precursor and reactant by simply operating an endpoint valve placed close to the ALD reactor, because the upstream pressure is controllable whether the gas flow is running or not.
We have demonstrated an ALD process with trimethylaluminum (TMA) and water vapor (H2O) reaction for Al2O3 deposition using the FCS to accurately control dosing into the ALD reactor. Excellent uniformity and reproducibility of deposition, and high quality dielectric properties of the resulting Al2O3 films have been achieved. The critical doses of TMA and H2O into the chamber have been found to achieve surface saturating ALD of Al2O3 on a silicon substrate.
[1] A. Guthrie, R. K. Wakerling, “Vacuum Equipment and Techniques” McGraw-Hill book company, Inc., pp17, (1949)
[2] R. H. Perry, D. Green, “Perry's Chemical Engineers' Handbook, Sixth Edition” McGraw-Hill Co., pp5-14, (1984)