Abstract:
Increasing the number of successive pulses of oxidant before applying pulses of metal precursor may improve the quality of the resulting metal or rare earth oxide films. These metal or rare earth oxide films may be utilized for high dielectric constant gate dielectrics. In addition, pulsing the oxidant during the pre-stabilization period may be advantageous. Also, using more pulses of oxidant than the pulses of precursor may reduce chlorine concentration in the resulting films.

Description:
BACKGROUND  
       [0001]     This invention relates generally to the deposition of transition metal and rare earth oxides.  
         [0002]     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.  
         [0003]     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.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a schematic depiction of an atomic layer deposition chamber in accordance with one embodiment of the present invention; and  
         [0005]      FIG. 2  is a depiction of a process sequence in accordance with one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0006]     Referring to  FIG. 1 , an atomic layer deposition device  10  may include a chamber  20  having heaters  18  surrounding the chamber. A wafer W to be exposed to production gases may be inserted within the chamber  20 . In one embodiment of the present invention, nitrogen gas (N 2 ) may continuously flow through the chamber  20  to a vacuum pump.  
         [0007]     A first precursor A may be contained in liquid form within a closed, pressurized, heated reservoir  12   b . The injection of the precursor A, as a gas, into the chamber  20  via the line  16   b  may be controlled by a high speed valve  14   b . In one embodiment of the present invention, the reservoir  12   b  holds an oxidant such as water, hydrogen peroxide, or ozone.  
         [0008]     A metal precursor may be stored in a closed, pressurized, heated reservoir  12   a . The metal precursor may, for example, be hafnium chloride (HfCl 4 ) 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  12   a  communicates with the chamber  20  via line  16   a , whose flow is controlled by a high speed valve  14   a.    
         [0009]     Due to the presence of the high speed valves  14   a  and  14   b , pulses of metal precursor or oxidant may be supplied to the chamber  20  in any desired sequence.  
         [0010]     Referring to  FIG. 2 , in accordance with one embodiment of the present invention, the formation of metal oxide films may be accomplished using a first pre-stabilization stage  22 , followed by a film deposition stage  24 , in turn followed by a post-stabilization stage  26 . In some embodiments of the present invention, the pre-stabilization stage  22  may be shortened relative to conventional techniques. In some embodiments, the pre-stabilization time at temperature may even be minimized before deposition begins, to maximize surface hydroxyl termination for the first cycles of dielectric film deposition.  
         [0011]     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.  
         [0012]     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.  
         [0013]     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.  
         [0014]     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.  
         [0015]     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.