Abstract:
Disclosed herein is a method for the fabrication of a capacitor of semiconductor device, which is capable of increasing a charge storage capacitance of the capacitor while generation of leakage current in the capacitor. The method comprises the steps of: forming a ruthenium film as a lower electrode on a semiconductor substrate; forming a TaON film having a high dielectric constant on the ruthenium film; and forming a upper electrode on the TaON film.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 2000-30089, filed Jun. 1, 2000, the entirety of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a method for the fabrication of a capacitor of a semiconductor memory device, and more particularly to a method of fabricating a capacitor of a semiconductor device, which is capable of increasing a charge storage capacitance of the capacitor while preventing generation of leakage current in the capacitor. 
     2. Description of the Related Art 
     With recent advances in semiconductor fabrication technology, the demand for memory devices had increased rapidly. In semiconductor devices, a capacitor being used as a data storage element is varied in its capacitance depending on the area of its electrodes, the distance between the electrodes, and the dielectric constant of the dielectric film interposed between the electrodes. 
     However, as the integration density of a semiconductor device is increased, the capacitor is reduced in the area that it occupies in the semiconductor device and thus is the area of its electrodes is reduced, thereby reducing its capacitance. 
     For this reason, to maximize the capacitance of the capacitor, the prior art includes depositing a ruthenium film as the lower electrode on a substrate, depositing a TaON film having high dielectric constant on the ruthenium film, and depositing a metal film on the dielectric film, thereby forming a capacitor structure of metal film-dielectric film-metal film (MIM). 
     FIGS. 1 a  and  1   b  show a fabricating method of a capacitor of a semiconductor device according to the prior art. As shown in FIG. 1 a,  on a semiconductor device  2  having a MOS transistor (not shown), there is formed an interlayer insulating film  4  having a contact hole (not shown) through which one of junction regions of the MOS transistor is exposed. 
     After this, a polysilicon film  5  for a plug is filled in the interlayer insulating film  4 , and then etched back to remove a native oxide film. Then, a Ti/TiN film  6  as a barrier metal film is deposited on the resulting substrate. 
     Afterwards, as shown in FIG. 1 b,  a ruthenium film  7  as a lower electrode is deposited on the barrier metal film  6  using an O 2  gas as a reaction gas. The O 2  gas used in this step makes the deposition of the ruthenium film  7  easy by breaking down the molecular structure of tris(2,4-octanedionato)ruthenium used as a ruthenium source. 
     Then, a TaON film  8  having a good dielectric constant is formed on the ruthenium film  7 . Next, an upper electrode  9  is formed on the TaON film  8  to complete a capacitor of a semiconductor memory device. 
     However, such a prior method for the fabrication of the capacitor suffers from problems as described below. 
     The prior method employs the O 2  gas in deposition of the ruthenium film as the lower electrode. This O 2  gas makes deposition of the ruthenium film  7  easy by breaking down the molecular structure of tris(2,4-octanedionato)ruthenium as a ruthenium source, but causes carbons to remain in the ruthenium film, thereby deteriorating electrical properties of the resulting capacitor. 
     Thus, in order to remove carbons present in the ruthenium film and improve properties of the ruthenium, the prior art performs a subsequent heat-treatment, such as Rapid Thermal Processing (RTP), under an atmosphere of N 2 , Ar or Ar/N 2 . This results in loss in fabricating time and economical efficiency. 
     SUMMARY OF THE INVENTION 
     The present invention solves prior problems as described above and provides a fabricating method of a capacitor of a semiconductor device, which can improve electrical properties of the capacitor. 
     Additionally, the present invention provides a fabricating method of a capacitor of a semiconductor memory device, which is capable of increasing a charge storage capacitance of the capacitor while preventing generation of leakage current in the capacitor. 
     In one embodiment, the present invention provides a method for the fabrication of a capacitor of a semiconductor device, comprising the steps of forming a ruthenium film as a lower electrode on a semiconductor substrate; forming a TaON film having a high dielectric constant on the ruthenium film; and forming an upper electrode on the TaON film. 
     In another embodiment, the present invention provides a method for the fabrication of a capacitor in a semiconductor device, comprising the steps of forming a ruthenium film as a lower electrode on a semiconductor substrate; forming an amorphous TaON film having a high dielectric constant on the ruthenium film; annealing the amorphous TaON film to form a crystalline TaON film; and forming an upper electrode on the crystalline TaON film. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a  and  1   b  are cross-sectional views describing a fabricating method of a capacitor of a semiconductor device according to the prior art; and 
     FIGS. 2 a  and  2   d  are cross-sectional views describing a fabricating method of a capacitor of a semiconductor device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of a fabricating method of a capacitor of a semiconductor device according to the present invention will now be described in detain with reference to the accompanying drawings. 
     FIGS. 2 a  and  2   d  are cross-sectional views describing a fabricating method of a capacitor of a semiconductor device according to the present invention. 
     Referring to FIG. 2 a,  on a semiconductor device  12  having a substrate and a MOS transistor (not shown), there is an interlayer insulating film  14  having a contact hole  13  through which one of junction regions (not shown) of the MOS transistor is exposed. 
     Then, a plug polysilicon film  15  is formed on the interlayer insulating film  14  in such a manner that it fills in the contact hole  13  of the interlayer insulating film  14 . Next, the polysilicon film  15  is etched back at its surface using a HF solution or a buffer oxide as an etching regent to remove a native oxide film. 
     Following this, on the resulting substrate, there are deposited a Ti film and a TiN film to a thickness of 100 Å to 500 Å, respectively, thereby forming a barrier metal film  16 . 
     As shown in FIG. 2 b,  on the barrier metal film  16  is deposited a ruthenium film  17  as a lower electrode. At this time, NH 3  gas is used as a reaction gas for deposition of the ruthenium film  17 . The use of NH 3  gas inhibits the amount of carbons present in the ruthenium film  17 . Also, this NH 3  gas serves as a Lewis base, so that it weakens a bond strength of CH groups present in the ruthenium film  17  during deposition, thereby removing easily the CH groups from the ruthenium film  17 . 
     During deposition of the ruthenium film  17  as the lower electrode, tris(2,4-octanedionato)ruthenium in vapor phase is used as a ruthenium source, and the semiconductor substrate  11  is maintained at a temperature of 200° C. to 350. Moreover, O 2  and NH 3  gases used as reaction gases for deposition of the ruthenium film  17  are maintained at a flow rate from several tens to several hundreds SCCM, and a reactor chamber is maintained at a pressure of several mTorr to several Torr. In addition, the ruthenium film  17  is preferably deposited to a thickness of 100 Å to 500 Å. 
     Then, as shown in FIG. 2 c,  on the ruthenium film  17  is deposited an amorphous TaON film  18 , as a dielectric film, which has an excellent dielectric constant. At this time, tantalum ethylate (Ta(OC 2 H 5 ) 5 ) is used as a tantalum source. As Ta(OC 2 H 5 ) 5  is present in liquid phase as known in the art, it must be supplied into a LPCVD chamber after being transformed into vapor phase. 
     For formation of the TaON film  18 , Ta(OC 2 H 5 ) 5  as the tantalum source is vaporized in a vaporizer at a temperature of 170 to 190° C. to produce a Ta chemical vapor. The Ta chemical vapor is reacted with a NH 3  gas in the LPCVD chamber which is maintained at a pressure of 0.1 to 1.2 Torr and at a temperature of 350 to 450° C. and into which the NH 3  gas is supplied at a flow rate of 10 to 1000 standard cubic centimeters per minute (SCCM). This reaction yields the amorphous TaON film  18 . 
     Then, as shown in FIG. 2 d,  the amorphous TaON film  18  is subjected to a RTP annealing for 1 to 5 minutes at a temperature 500 to 700° C. under an atmosphere of N 2  or O 2 , thereby forming a crystallized TaON film  18   a.    
     Then, on the TaON film  18   a  is deposited an upper film, such as a TiN film  19  or a metal film, to complete a capacitor of a semiconductor device. 
     Meanwhile, the method of the present invention may also be applied to the fabrication of a cylinder-type, stack-type, or trench-type capacitor, etc. without departing the sprit and scope of the present invention. 
     As apparent from the foregoing, the method of the present invention employs a NH 3  gas instead of an O 2  gas as the reaction gas, upon formation of the ruthenium film as the lower electrode. This inhibits the amount of carbons present in the lower electrode, thereby improving the electrical properties of the resulting capacitor. In addition to this advantage, as the method of the present invention does not require a subsequent annealing process of removing carbons from the lower electrode, it can reduce fabricating time and cost. 
     Further, the method of the present invention forms the TaON film having an excellent dielectric constant on the lower electrode. This can meet an increasing demand for memory devices and a requirement for a high capacitance per a small capacitor area. 
     Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.