JPS5917279A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enable to reduce sharply leakage current, to reduce the area of a capacitor, and to enhance the degree of integration of the device by a method wherein the device is constructed by depositing an insulating film having high permittivity on an N type Si substrate containing impurities in high concentration, and forming a metal electrode thereon. CONSTITUTION:After Ar gas of 5X10<-3>Torr is flowed to an Si substrate 1 and presputtering is perfomred, electric discharge of about 1.5kW power is generated under gas pressure of 5X10<-3>Torr of mixed gas of Ar and O2, and Ta2O5 of about 10nm thickness is deposited on the Si substrate 1. The measured value of interfacial level density (containing the influence of fixed electric charge in the film) QSS is obtained as such high density of 5X10<13>cm<-2> at Ta2O5 deposited as to form N type 10OMEGAcm resistance under the above-mentioned condition. The value of the leakage current to flow when the capacitor constructed by evaporating the metal electrode 3 of Al, etc. to constitute a confronting electrode on Ta2O5 2 formed by this way is used, and the respective leakage currents when a positive voltage and a negative voltage are applied are reduced to the small values as shown with the curves 4, 5, 6 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor structure using a high dielectric constant insulating material made of a metal oxide such as tantalum oxide, niobium oxide, titanium oxide, etc., and particularly to a capacitor with a small leakage current. Regarding preferred construction.

In conventional capacitors using high dielectric constant insulating films such as tantalum oxide, metals such as Ni and Cr are used for the electrodes. When tantalum oxide is used, tantalum nitride is also used as the N electrode. However, since the leakage current is larger than that of the S j Ox film, it has the disadvantage that it cannot be used in capacitors that are subject to high electric fields, such as conventional large-scale integrated circuits (LSI).

The purpose of the present invention is to eliminate such drawbacks of the conventional technology, and by creating a capacitor with a high withstand voltage, it is possible to apply it to minute capacitors in LSIs such as dynamic random access memories. The purpose of this invention is to provide a new technology that enables the application of high dielectric constant insulating films.

A high dielectric constant insulating film was deposited on an n-type Si substrate containing a high concentration of impurities, and the leakage current was measured using a capacitor with metal electrodes formed entirely on it. Compared to a capacitor of conventional structure sandwiched between the two, the leakage current was reduced to +lj.

This is because the Schottky barrier between the oxide film and the electrode becomes larger when St is used compared to a metal electrode, and a heavy-density interface state is formed at the interface between silicon and the insulating film, and this interface ratio XT is It is thought that the more leakage current is captured, the more the leakage current decreases.

EXAMPLE Hereinafter, an example of the present invention will be explained with reference to FIG. In this embodiment, tantalum oxide ('pa2Qs) is used as a high dielectric constant insulating film serving as a dielectric of the capacitor. 1st,
As shown in Figure 1, n-type Si1 contains a high concentration of impurities.
']:'a2Qs 2 is deposited using a sputtering method or the like. At this time, the sputtering temperature was 13.56MH2.
Using a sputtering device, use argon (Ar) using a metal Ta plate as a target.

A reactive sputtering method was used to form Ta2Q5 in a mixed gas of and oxygen (02). The sputtering conditions and procedures are described below. The n-type Si substrate on which Ta205 was deposited was first subjected to a cleaning process of washing with water, surface oxidation in boiling nitric acid, and removal of surface oxide with dilute hydrofluoric acid. Place the Si substrate in a sputtering device, 5 x 1
After pulling to a high vacuum of 0-”porr, 5 x 10-”
Sputtering is performed for about 20 minutes to remove the contaminant layer on the target surface, which is called pre-sputtering by flowing l'orrQAr gas. After the press sputtering is completed, the vacuum is again drawn to a high vacuum and Ar and 02 are flowed. At this time, the partial pressure of 02 should be about 10 to 20% of the total pressure. After the gas pressure becomes sufficiently stable, discharge begins. At this time, the mixed gas pressure of Ar and 02 is 5
It was performed at 10-J7orr.

The discharge was performed with a power of about 1.5 kW, and about 1100 nm of 'I'a2Qs was deposited on the Si substrate. The interface state density (including the influence of identified charges in the film) Qss is n-type 1
0, Q cm deposited under the above conditions.
2 Q s and a high density Q, ss of 5 X 10” cm −2 was measured.

On the thus formed TazQs, an opposing layer of At, etc., and a gold cloud 3 serving as a pole are vapor-deposited to form a capacitor. Using this capacitor leak 'fkt Ml
In FIG. 2, 4 is the capacitor structure shown in FIG.
The leakage current in a capacitor in which At is first deposited, Ta2O52 is further deposited, and At3 is further deposited is shown.

Further, 5 indicates a leakage current when a positive voltage is applied to the capacitor having the structure shown in FIG. 1, and 6 indicates a leakage current when a negative voltage is applied.

As is clear from this, it can be seen that the leakage current is small in the capacitor having the structure shown in FIG. In addition, Table 1 also shows the first
Figure shows the capacitance of a capacitor with a structure.

It is clear that the frequency dispersion of the capacitance is negligible and the ugliness δ is also small.

1st coating film thickness: 1000 people Electrode area: 2 x 10-''cm2 As described above, according to the present invention, it is possible to significantly reduce the leakage current of a capacitor using a high dielectric constant insulating film such as Ta205. Therefore, if the present invention is used,
Conventionally, high dielectric constant insulation f, which was difficult to replace as a capacitor in dynamic random access memory due to its large leakage current, can now be applied, making it possible to reduce the area of the capacitor and greatly increasing the degree of integration. It has the effect of improving.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a capacitor using the present invention, FIG. 2 is a leakage current characteristic measured using the capacitor shown in FIG. 1, and Table 1 shows frequency dependence of dielectric constant and dielectric loss. DESCRIPTION OF SYMBOLS 1...n-type Si substrate, 2...high 6-concentration loquat film, 3...
・Written amendment for money procedure (method) Indication of the case Patent application No. 325694 of 1982 Name of the invention Semiconductor device Person making the amendment... 1. , 751'llll'+, Ceremony 111', 'i'
2? '+3 1) Shigeyo Katsu
Rito's name (7237) BU■〒 1: Usui 1) Ri'yuki, date of 1 correction order σ
October 26, 1980 ゛Amended χ-j Column for a brief explanation of the drawings in the specification Figure 2 shows the dependence. ] "Figure 2 is a curve diagram showing the leakage weighting characteristics obtained by measurement using the capacitor shown in Figure 1. JKNI correct.

Claims (1)

[Claims] 1. In a capacitor whose dielectric is a metal oxide high dielectric constant insulating material, at least one of the electrode materials is n-type silicon with a high impurity concentration, and the above-mentioned high-place-4 insulating material and the above-mentioned n-type 7 silicon film are used. A semiconductor device characterized by the formation of high-resolution interface states in the field (river).