JPH0746669B2 - Thin film capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a thin film capacitor comprising a lower electrode, a dielectric and an upper electrode which are sequentially formed on a substrate, and more particularly, at least one of the lower electrode and the upper electrode comprises a conductive layer composed of a plurality of layers. And a thin film capacitor having a structure in which at least one conductive layer in contact with a dielectric among a plurality of conductive layers is made of a conductive metal oxide film.

[0002]

2. Description of the Related Art Conventionally, a thin film capacitor of this type has a structure in which a dielectric film and an upper electrode are sequentially formed on a silicon electrode by a sputtering method (Japanese Patent Application No. 1-217918).
Or at least one of Ta, Ti, etc. on the silicon electrode
A structure in which a dielectric film and an upper electrode are sequentially formed on a conductive layer composed of a first layer made of a kind of refractory metal and a second layer made of at least one kind of material of Pt and Pd (Patent application 1 -238484). Also, for example, 1969 I Bem Journal of Research and Development, Volume 68, 68.
Pages 6-695 (IBM Journal of Research and Dev
lopment, 68 (1969), p.686-695), a structure in which Pt or Pd is deposited as a lower electrode on an insulating substrate such as sapphire, and a dielectric film and an upper electrode are formed in this order. Already known.

[0003]

In the thin film capacitor having the conventional structure described above, when the dielectric is directly formed on the silicon electrode by the sputtering method, the surface of the silicon electrode is oxidized when the dielectric is formed. However, even if a dielectric having a high dielectric constant is formed, there is a drawback in that the capacitance of the whole thin film capacitor is limited due to the low dielectric constant silicon dioxide existing at the interface between the silicon electrode and the dielectric. However, the presence of the silicon dioxide layer has an advantage that the leak current does not become too large. Also,
In the case of a structure in which a conductive layer made of the first and second materials is formed on the silicon electrode, and a dielectric and an upper electrode are sequentially formed on the conductive layer, a suitable heat treatment is performed to form the low dielectric constant layer. Although it is possible to increase the capacitance of the entire thin film capacitor while preventing the formation, it becomes impossible to suppress the leak current flowing in the dielectric film, and especially when the thickness of the dielectric film is 50 nm or less. If such a thin film is used, there is a disadvantage that carrier tunneling occurs and the amount of leak current increases. The present invention has been made in order to solve the above-mentioned conventional problems, and has a large capacity and a read capacity.
It is an object of the present invention to provide a thin film capacitor with a low dc current.

[0004]

The present invention comprises a lower electrode,
In a thin film capacitor in which a dielectric and an upper electrode are sequentially formed, at least one of the lower electrode and the upper electrode is composed of a plurality of conductive layers, and one of the lower electrode and the upper electrode is a plurality of conductive layers, and In a thin film capacitor characterized in that a conductive layer in contact with the dielectric is made of a conductive metal oxide film, and a thin film capacitor in which a lower electrode, a dielectric and an upper electrode are sequentially formed, a lower electrode and an upper electrode A thin film capacitor characterized in that both are composed of a plurality of conductive layers, and two conductive layers in contact with the dielectric are composed of a conductive metal oxide film.

[0005]

In the thin film capacitor of the present invention, a large capacitance is realized by preventing the formation of the low dielectric constant layer, and
In order to form a capacitor with a small electric current, by using a conductive metal film as the layer in contact with the dielectric film among the conductive layers consisting of multiple layers, the barrier effect against electrons or holes is utilized. It has a structure that reduces the leak current.
At this time, when only the conductive layer of one electrode composed of a plurality of conductive films in contact with the dielectric film is a conductive metal oxide film, the leak current amount has a polarity, so that the leak current amount is small. To suppress it, the polarities of the voltages applied to the upper and lower electrodes are fixed. On the other hand, the leak current can be reduced regardless of the polarity of the applied voltage by using both the upper and lower electrodes made of a plurality of conductive layers in contact with the dielectric film as conductive metal oxide films.

[0006]

Embodiments of the present invention will now be described with reference to the drawings. Example 1 FIG. 1 is a longitudinal sectional view of an example of a thin film capacitor according to the present invention using SrTiO ₃ as a dielectric. In the figure, 1 is an Au film, 2 is a Ti film, 3 is SrTiO ₃ , 4 is PdO, 5 is Pt, 6 is Ta, and 7 is a low resistance silicon substrate. The Au and Ti films 1 and 2 constitute an upper electrode, and the PdO, Pt, Ta and silicon substrates 4 to 7 form a lower electrode. The fabrication process used a known thin film deposition technique as follows. First, Ta6 and Pt5 are sequentially formed on the silicon substrate 7 in the order of 10 to 150 n, respectively.
m to a thickness of 20 to 150 nm by a direct current magnetron sputtering method, and then Ar / as a sputtering gas.
The PdO4 using a mixed gas of O ₂ is deposited to a thickness of 5~150nm by reactive DC magnetron sputtering to form a lower electrode. Further, the SrTiO ₃ film 3 is deposited to a thickness of 30 to 500 nm by the high frequency magnetron sputtering method. Finally, as the upper electrode, 1 each of Ti2 and Au1 was formed by the DC magnetron sputtering method.
The thin film capacitors shown in FIG. 1 were manufactured by depositing the films with a thickness of 0 to 150 nm and 100 to 500 nm. In the thin film capacitor having the structure shown in FIG. 1, when the upper electrode is set to a positive voltage and the lower voltage is set to a negative voltage, the leak current flowing through the thin film capacitor is small, but when the reverse voltage is applied, the leak current is large. .

Embodiment 2 FIG. 2 is a vertical sectional view of another embodiment of the present invention. 1 in the figure
1 is an Au film, 12 is a Ti film, 13 and 15 are PdO,
14 is SrTiO ₃ , 16 is Pt, 17 is Ta, and 18 is a low resistance silicon substrate. The manufacturing process is similar to that of the thin film capacitor of FIG.
The conductive layer in contact with rTiO ₃ is PdO having a thickness of 5 to 150 nm.
Is different. The thin film capacitor having the structure of FIG. 2 has a small leak current regardless of the polarities of the voltages applied to the upper and lower electrodes, which is an advantage different from the thin film capacitor of FIG. Although PdO is used as the conductive metal oxide film in each of the above-described embodiments, conductive TaO _x , SrTiO _x, or the like can also be used.

[0008]

As described above, according to the present invention,
By using a conductive metal oxide film as the conductor layer in contact with the dielectric film of one or both of the lower electrode and the upper electrode,
There is an effect that the leak current can be reduced depending on whether the applied voltage is unipolar or bipolar.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a thin film capacitor according to the present invention.

FIG. 2 is a vertical sectional view of another embodiment of the thin film capacitor according to the present invention.

[Explanation of symbols]

1,11 Au 2,12 Ti 3,14 SrTiO ₃ 4,13,15
PdO 5,16 Pt 6,17 Ta 7,18 Silicon substrate

Claims (2)

[Claims] 1. In a thin film capacitor in which a lower electrode, a dielectric and an upper electrode are sequentially formed, at least one of the lower electrode and the upper electrode comprises a plurality of conductive layers, and either the lower electrode or the upper electrode. One is a plurality of conductive layers, and the conductive layer in contact with the dielectric is PdO, TaO _x ,
A thin film capacitor comprising at least one conductive metal oxide film selected from SrTiO _x . 2. In a thin film capacitor in which a lower electrode, a dielectric and an upper electrode are sequentially formed, both the lower electrode and the upper electrode are composed of a plurality of conductive layers, and the two conductive layers in contact with the dielectric are PdO, TaO _x , SrTiO _x
A thin film capacitor comprising at least one conductive metal oxide film selected from the group consisting of: