Patent Application
20060045968
This invention relates generally to the deposition of transition metal and rare earth oxides.
Transition metal and rare earth oxides may be deposited as gate oxides for metal gate field effect transistor integrated circuits. Conventional atomic layer deposition of transition metal and rare earth oxide may be disadvantageous. One problem with some existing processes is that the chlorine concentration in the resulting film may be high. Chlorine can lead to degradation of the dielectric constant and may promote reactions with the gate electrode, degrading device performance and decreasing reliability. The inclusion of chlorine into the dielectric lattice may result in the formation of oxygen vacancies, which may degrade the effectiveness of the gate oxide.
Thus, there is a need for better ways to form high dielectric constant transition metal and rare earth oxides, for example, for forming gate dielectrics for metal gate electrode semiconductors.
Referring to
A first precursor A may be contained in liquid form within a closed, pressurized, heated reservoir 12b. The injection of the precursor A, as a gas, into the chamber 20 via the line 16b may be controlled by a high speed valve 14b. In one embodiment of the present invention, the reservoir 12b holds an oxidant such as water, hydrogen peroxide, or ozone.
A metal precursor may be stored in a closed, pressurized, heated reservoir 12a. The metal precursor may, for example, be hafnium chloride (HfCl4) in connection with forming a hafnium oxide metal dielectric film. Other metal precursors include any of the transition metal and rare earth oxides including those suitable for forming high dielectric constant gate oxides such as hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. As used herein, a high dielectric constant oxide is one with a dielectric constant of at least ten. The reservoir 12a communicates with the chamber 20 via line 16a, whose flow is controlled by a high speed valve 14a.
Due to the presence of the high speed valves 14a and 14b, pulses of metal precursor or oxidant may be supplied to the chamber 20 in any desired sequence.
Referring to
During the pre-stabilization stage 22, the wafer W is loaded into the chamber 20, as indicated at 21. A pulse of oxidant (A) may be followed by a short purge cycle (P). This oxidant/purge sequence may be repeated four or more times in some embodiments. During the pre-stabilization stage, the wafer W is being heated and the chamber 20 is being prepared for film deposition. In one embodiment, the pre-stabilization stage may use water as the oxidant. Thus, a purge cycle may follow each oxidant pulse. Providing the oxidant during the pre-stabilization stage may increase surface hydroxyl termination for early stages of film growth in some embodiments.
After the pre-stabilization stage 22, a series of pulses of the oxidant A may each be followed by a purge. Thus, in the illustrated embodiment, three pulses of oxidant A, followed by three purges, are implemented. However, the repeat of times one is subject to great variability. In some embodiments of the present invention, it is desirable to have two times the number of pulses of the oxidant relative to the number of pulses of the metal precursor. Increasing the number of oxidant pulses may reduce the chlorine concentration in the resulting metal oxide film. The pulse width may be selectable in accordance with conventional procedures.
After a series of pulses of the oxidant, a series of pulses of the metal precursor B, each followed by a purge, may be implemented. In some embodiments, the number of pulses of oxidant may be higher than the number of pulses of the metal precursor. The number of pulses of the metal precursor may be determined by the desired film thickness. By pulsing the same precursor multiple times in succession, layer-to-layer reactions can be pushed further towards completion, resulting in films closer to ideal composition, with fewer defects, leading to higher performance gate dielectrics in some embodiments.
For example, in connection with hafnium chloride as the metal precursor, providing two water pulses for each hafnium chloride pulse may decrease the chlorine concentration in the resulting hafnium oxide films by two to three times.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
