JPH0917949A - High dielectric constant film capacitor - Google Patents

Abstract

PURPOSE: To reduce leakage current using an amorphous phase and improve dielectric constant characteristics by placing the amorphous phase in the grain boundary of a high dielectric constant film of polycrystalline structure placed between a pair of electrodes. CONSTITUTION: A high dielectric constant capacitor has a high dielectric constant film 14 between a pair of electrodes 13, 17. The high dielectric constant film 14 is of polycrystalline structure and composed of crystal grains. A crystal phase 15 and an amorphous phase 16 are present together in the high dielectric constant film, and thus the high dielectric constant film is of such crystal grain structure that a crystal grain boundary is destroyed by the amorphous phase 16. Since the crystal boundary, which forms a predominant point of current leakage in the high dielectric constant film 14, is destroyed by the amorphous phase 16, as mentioned above, leakage current is minimized when voltage is applied between the upper and lower electrodes 13, 17. Moreover, since the amorphous phase 16 covers the crystal grains in the high dielectric constant film 14, the crystal phase 15 ensures dielectric constant between the electrodes 13, 17, which prevents degradation in the dielectric constant of the entire film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor using a polycrystalline high dielectric constant film.

[0002]

2. Description of the Related Art Hitherto, a high dielectric constant film capacitor has a polycrystalline high dielectric constant film provided between a pair of electrodes. However, when the high dielectric constant film has a polycrystalline structure, the leakage current due to the crystal grain boundary is large, and it is difficult to obtain a desired capacitor capacity. Capacitors provided with a high dielectric constant film having a multilayer structure of a phase and an amorphous phase have been developed.
29472).

[0003]

However, in the above-mentioned conventional capacitor, the dielectric constant of a film having an amorphous structure is generally smaller than the dielectric constant of a film having a crystalline structure. There is a problem that the dielectric constant is lower than that in the case of only the crystal phase.

An object of the present invention is to provide a high-dielectric-constant film capacitor in which the leakage current is suppressed to a small value and the dielectric constant characteristics are improved.

[0005]

In order to achieve the above object, a high dielectric constant film capacitor according to the present invention is a high dielectric constant film capacitor having a high dielectric constant film between a pair of electrodes. The dielectric film has a polycrystalline structure composed of crystal grains, and the crystal grains are covered with a high-dielectric-constant film at mutual crystal grain boundaries.

The high dielectric constant film covering the crystal grains is
It is a dielectric constant film having an amorphous structure.

[0007] Some of the crystal grains forming the high dielectric constant film are bonded to the electrode.

The high dielectric constant film having the amorphous structure is provided in a columnar shape over a pair of electrodes, and a high dielectric constant film having a polycrystalline structure is provided between adjacent columnar high dielectric constant films. Is what it is.

The high dielectric constant film having a polycrystalline structure is bonded to a pair of electrodes.

[0010]

The amorphous phase is interposed in the crystal grain boundary of the polycrystalline high dielectric constant film provided between the paired electrodes, and the leakage current caused by the crystal grain boundary is suppressed by the amorphous phase.

The dielectric constant between the paired electrodes is ensured by a high dielectric constant film having a polycrystalline structure.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing Embodiment 1 of the present invention.

In FIG. 1, a high dielectric constant film capacitor according to the present invention has a high dielectric constant film 14 between a pair of electrodes 13 and 17 as a basic configuration. The high-dielectric-constant film 14 has a polycrystalline structure composed of crystal grains, in which a crystal phase 15 and an amorphous phase 16 are mixed to form a crystal grain structure in which the crystal grain boundaries are eliminated by the amorphous phase 16. To hold. A specific example will be described.

A lower electrode 13 is formed on a thermal oxide film 12 previously formed on a silicon substrate 11 by platinum sputtering or the like.

Further, the substrate 11 on which the lower electrode 13 is formed
A high dielectric constant film 14 such as strontium titanate (SrTiO ₃ ) is formed thereon. At this time, for example, the crystallographic structure of the film to be formed is changed by controlling the flow ratio of the source gas. In particular, under a growth condition in which the composition ratio of Sr to Ti maintains a stoichiometric composition such as 1, a film having a crystal structure is formed, which has a polycrystalline structure separated by crystal grain boundaries. On the other hand, S for Ti
As the composition ratio of r becomes smaller than 1, the crystal structure of the film changes to an amorphous structure.

For this embodiment, T is used for LPCVD.
By setting the flow rate of the i source gas higher than the flow rate of the Sr source gas and using a growth condition in which a crystal grain structure and an amorphous structure are simultaneously formed in the high dielectric constant film 14,
A crystal phase 15 of SrTiO ₃ and an amorphous phase 16 covering a crystal grain boundary of the crystal phase 15 are mixed. Part of the crystal phase 15 is in contact with the lower electrode 13.

Further, an upper electrode 17 is formed on the high dielectric constant film 14 in which the crystalline phase 15 and the amorphous phase 16 are mixed by platinum sputtering or the like. Some of the crystal phases 15 are the upper electrode 1
7.

According to the present embodiment, when a voltage is applied to the upper and lower electrodes 13 and 17, a crystal grain boundary which is a site of a dominant current leak in the high dielectric constant film 14 is eliminated by the amorphous phase 16. Therefore, the leakage current can be reduced.

The amorphous phase 16 is a high dielectric constant film 14
Of the high dielectric constant film 14, and the crystal phase 15 of the high dielectric constant film 14 secures a dielectric constant between the electrodes 13 and 17. Does not decrease.

(Embodiment 2) FIG. 2 is a sectional view showing Embodiment 2 of the present invention.

In this embodiment, the amorphous phase 16 is grown in a columnar shape between the electrodes 13 and 17 in the high dielectric constant film 14 and the crystal grain size of the crystalline phase 15 is increased between the adjacent amorphous phases 16. Thus, the crystal phase 15 is directly bonded to the electrodes 13 and 17. At this time, by decreasing the substrate temperature and controlling the composition ratio of the raw materials supplied during the growth, the crystal grain size of each of the high dielectric constant films is increased.

According to the present embodiment, the crystal phase 15 is
Since they are directly bonded to the electrodes 3 and 17, the voltage from the electrodes 13 and 17 can be uniformly applied to the crystal grains of the crystal phase 15, and a higher dielectric constant can be obtained.

In this embodiment, a silicon wafer is used, but an SOS (Sil) having silicon only on its surface is used.
icon on Sapphire) or SOI (Sil)
(icon on Insulator) substrate may be used. The electrodes 13 and 17 are not limited to platinum but may be polycrystalline silicon or the like. The high dielectric constant film 14 is made of SrTiO ₃
Not limited to this, tantalum oxide (Ta ₂ O ₅ ), lead zirconate titanate (PZT), or the like may be used.

[0025]

As described above, according to the present invention, it is possible to provide a high dielectric constant capacitor which can reduce the leak current while maintaining the high dielectric constant of the high dielectric film and has a long charge accumulation time. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

 11 silicon substrate 12 thermal oxide film

Claims (5)

[Claims] 1. A high dielectric constant film capacitor having a high dielectric constant film between a pair of electrodes, wherein the high dielectric constant film has a polycrystalline structure composed of crystal grains. A high dielectric constant film capacitor characterized by being covered with a high dielectric constant film at a portion of a crystal grain boundary. 2. The high dielectric constant film capacitor according to claim 1, wherein the high dielectric constant film covering the crystal grains is a dielectric constant film having an amorphous structure. 3. A part of crystal grains constituting the high dielectric constant film,
The high dielectric constant film capacitor according to claim 1, wherein the high dielectric constant film capacitor is bonded to the electrode. 4. The high dielectric constant film having an amorphous structure,
2. The high dielectric constant film according to claim 1, wherein a high dielectric constant film having a polycrystalline structure is provided between adjacent electrodes in a columnar shape, and between adjacent columnar high dielectric constant films. Dielectric film capacitor. 5. The high-dielectric-constant film capacitor according to claim 1, wherein the high-dielectric-constant film having a polycrystalline structure is bonded to electrodes forming a pair.