Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Utility Patent
1999-07-07
2001-01-02
Bowers, Charles (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C438S239000, C438S253000, C438S396000, C438S381000, C257S295000, C257S296000, C257S310000
Utility Patent
active
06169305
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device, more specifically to a semiconductor device including a capacitor.
FeRAM (Ferro-electric Random Access Memory) is nonvolatile semiconductor memory using ferro-electric as the capacitors. FeRAM is much noted because of its high speed, low electric power consumption and repeatability characteristics.
In the process for forming a ferro-electric capacitor, oxygen annealing is performed for higher crystallization of the ferro-electronic film after the electrodes have been formed.
Accordingly, it is necessary that the electrodes of the ferro-electric capacitor are formed of a material which is free from oxidation by the oxygen annealing and lowering the conductivity or does not deprive oxygen of the ferro-electric film to lower electric characteristics of the capacitor. Al, Ti, W, etc. which are widely used as electrode materials in the general semiconductor devices, are oxidized by the oxygen annealing or deprive oxygen of the ferro-electric film, and are not suitable for the electrodes of the ferro-electric capacitor.
Then, it is proposed to use Pt, which is not oxidized by the annealing in an oxygen atmosphere, as an electrode material of the ferro-electric capacitor.
However, in a case that the electrodes of the ferro-electric capacitor are formed of Pt, when an electric field is repeatedly applied to the ferro-electric film, a remanence value lowers as times of the application of the electric field increase, and good fatigue characteristics cannot be obtained.
Then, it is proposed that the electrodes of the ferro-electric capacitor are formed of a metal oxide, such as IrO
2
, which is an electrode material providing good fatigue characteristics. Metal oxides, such as IrO
2
, etc., neither decrease the conductivities due to oxidation by the oxygen annealing, nor deprive oxygen of the ferro-electric film to thereby degrade electric characteristics of the capacitor.
However, in a case that a lower electrode of the ferro-electric capacitor is formed of IrO
2
film, electric characteristics of the ferro-electric capacitor, such as spontaneous polarization, leakage current, etc., are degraded. This will be because the ferro-electric film formed on the lower electrode of such metal oxide, which is inferior to the usual metals in crystallization cannot have good crystallization. In a case that the upper electrode of the ferro-electric capacitor is formed of a metal oxide, such IrO
2
or others, at the contact of the upper electrode with a line of Al, TiN or others, the Al or TiN deprives oxygen of the upper electrode and is oxidized, and a contact resistance is increased.
Thus, in a case that the electrode material is a metal oxide, it is preferable that a metal which is not oxidized by the annealing in an oxygen atmosphere, is formed on the metal oxide. Then, the Pt/IrO
2
electrodes are proposed. By using the Pt/IrO
2
electrodes the capacitor can have good electric characteristics, and the increase of a contact resistance can be prevented. In addition, the ferro-electric film can have improved fatigue characteristics.
However, the Pt/IrO
2
stacked electrode has poor adhesion at the interface between the Pt film and the IrO
2
film, and the Pt film often releases from the IrO
2
film. This is an obstruction to improvement of fabrication yields of the FeRAMs.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor device including the electrodes of the capacitor which are stacked in good adhesion, and a process for fabrication of the semiconductor device.
The above-described object is achieved by a semiconductor device comprising: an electrode which includes a first conductive film formed of an oxide film of a first metal, a second conductive film formed on the first conductive film and formed of the first metal, and a third conductive film formed on the second conductive film and containing a second metal different from the first metal. The second conductive film is sandwiched between the first conductive film and the third conductive film, whereby adhesion of the third conductive film can be improved, and the release of the third conductive film can be prevented.
In the above-described semiconductor device it is preferable that the electrode further includes a fourth conductive film formed below the first conductive film and formed of the first metal. The fourth conductive film having good adhesion with the substrate is formed below the first conductive film, whereby adhesion of the first conductive film to the substrate can be improved, and accordingly adhesion of the substrate to the electrode can be improved.
The above-described object can be achieved by a semiconductor device comprising: a capacitor including a lower electrode, a dielectric film formed on the lower electrode and an upper electrode formed on the dielectric film; the lower electrode and/or the upper electrode being composed of the above-described electrode. The second conductive film is sandwiched between the first conducive film and the third conductive film, whereby adhesion of the third conductive can be improved, and accordingly release of the third conductive film can be prevented. The semiconductor device can have the electrodes of a capacitor having high adhesion.
The above-described object can be achieved by a semiconductor device comprising: an electrode including a first conducive film formed of an oxide film containing a first metal, a second conductive film formed on the first conductive film and formed of an oxide film containing a second metal different from the first metal, and a third conductive layer formed on the second conductive film and containing the second metal. The second conductive film has low film stress, whereby a number of particles sticking to the wafer can be depressed, and the semiconductor device can have improved fabrication yields.
In the above-described semiconductor device it is preferable that the second conductive film has an oxygen composition ratio which decreases gradually away from the interface thereof with the first conductive film. It can be suppressed that oxygen composition ratios are uninterrupted between the second conductive film and the third conductive film. The electrode can have good adhesion.
The above-described object is achieved by a semiconductor device comprising: a capacitor including a lower electrode, a dielectric film formed on the lower electrode and an upper electrode formed on the dielectric film, the lower electrode and/or the upper electrode being composed of the above-described electrode. The second conductive film has small film stress, whereby a number of particles sticking to the wafer can be suppressed, and accordingly the semiconductor device can have improved fabrication yields.
The above-described object is achieved by a process for fabricating a semiconductor device comprising the step of forming a first conductive film formed of an oxide film containing a first metal, the step of forming a second conductive film formed of an oxide film containing a second metal different from the first metal and having an oxygen composition ratio which decreases gradually away from the interface thereof with the first conductive film, and the step of forming a third conductive film formed on the second conductive film and containing the second metal, in the step of forming the second conductive film the second conductive film being formed with an oxygen concentration in a deposition chamber gradually decreased. The second conductive film having an oxygen composition ratio which decreases gradually away from the interface thereof with the first conductive film can be formed, whereby interrupted oxygen composition ratios between the second conductive film and the third conductive film can be depressed. Accordingly electrodes having good adhesion can be formed, and accordingly a semiconductor device having a capacitor of good adhesion can be fabricated.
REFERENCES:
patent: 5905278 (1999-05-01), Nakabayashi
patent: 5976928 (1999-05-01)
Kondo Kazuaki
Takai Kazuaki
Armstrong, Westerman Hattori, McLeland & Naughton
Bowers Charles
Fujitsu Limited
Lee Hsien-Ming
LandOfFree
Semiconductor device and method for fabricating the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device and method for fabricating the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device and method for fabricating the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2527022