JPH01283862A - Semiconductor device - Google Patents

Abstract

PURPOSE:To suppress reaction of a capacity film with an electrode due to a heat treatment after the electrode is formed and to eliminate an increase in a leakage current of the capacity film and the deterioration of a dielectric breakdown strength by interposing metal nitride having chemical stability and small specific resistance between the electrode of the capacity and the capacity film. CONSTITUTION:A Ta2O5 film 2 of a capacity film, a titanium nitride layer 3, and a polycrystalline silicon layer 4 of a conductor layer are sequentially laminated on a silicon substrate. An electrode is formed of two layers of a titanium nitride layer 3 and a polycrystalline silicon layer 4. Thus, when the layer 3 is inserted between the layer 2 and the layer 4, the titanium nitride layer effectively prevents a reaction between the polycrystalline silicon and the Ta2O5, thereby largely reducing a leakage current by more than several orders of magnitude. Thus, pinholes or weak spots generated at the layer 2 of the capacity film are suppressed to suppress an increase in the leakage current of the capacity film, the deterioration of a breakdown strength and a decrease in reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device having a capacitive portion.

[Conventional technology]

such as dynamic random access memory,
The degree of integration of semiconductor devices that include capacitors as constituent elements is increasing year by year. Conventionally, high integration has been achieved by miniaturizing wiring and circuit element patterns. However, such miniaturization reduces the amount of accumulated charge corresponding to a signal, which is not preferable in terms of preventing memory malfunctions (soft errors) caused by radiation such as alpha rays.

Conventionally, this problem has been solved by making the dielectric layer of the capacitor thinner and increasing the capacitance value of the memory cell. However, as dielectric layers become thinner, for example, 6 nm 5i02
When a voltage of 5 .mu. is applied to the layer, a tunnel current flows, so there is a problem that it cannot be used as an insulating film in principle. Therefore, in order to obtain a large capacitance value with a small area occupied by the capacitor, T
a205, 'r'i02, Nb205, HfO2
.

Attempts have been made to use dielectric layers such as ZrO2.

The structure of the capacitive part using these dielectric layers is such that the dielectric layer is provided on a silicon substrate or a high melting point metal electrode such as tungsten, and the upper electrode is made of a high melting point metal, silicide, or polycrystalline silicon. is being attempted.

[Problem to be solved by the invention]

The conventional capacitor structure described above has a drawback in that leakage current increases during various heat treatments after manufacturing the capacitor section. This increase in leakage current is caused by a reaction occurring between the capacitive film (dielectric film) and the capacitive electrode part due to heat treatment, which deteriorates the film quality.
Alternatively, it may be caused by pinholes or areas with poor electrical insulation occurring locally. Therefore, there is a problem that the conventional capacitor structure cannot be used in an actual device.

[Means to solve the problem]

The semiconductor device of the present invention includes a first electrode made of a semiconductor layer or a conductive layer formed on a substrate, and a dielectric layer made of a metal oxide having a valve action provided on the first electrode. , an insulating layer made of a metal nitride or metal oxide layer and covering the dielectric layer, and a second electrode provided on the insulating film opposite to the first electrode. It has a department.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

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

A '1'a205 film 2 as a capacitive film, a titanium nitride layer 3, and a polycrystalline silicon layer 4 as a conductive layer are sequentially deposited on a silicon substrate. The electrodes are a titanium nitride layer 3 and a polycrystalline silicon layer 4.
It consists of layers.

This first example capacitor is manufactured as follows.

First, reactive sputtering or CVD is applied onto the silicon substrate 1.
The Ta205 layer 2 is deposited to a thickness of 5 to 30 nm by a method such as Depositing a Ta205 layer, or by a method of depositing a Ta layer by sputtering and then thermally oxidizing it to deposit Ta2051. Next, a titanium nitride layer 3 is formed on the Ta205 layer 2 by directly depositing a titanium nitride layer by sputtering, or by depositing a titanium layer by sputtering and then subjecting it to heat treatment such as lamp annealing. 30-200
It is deposited to a thickness of approximately 300 ml. Next, using a method such as CVD, a polycrystalline silicon layer 4 of 100% is deposited on the titanium nitride layer 3.
It is deposited to a thickness of about 0 to 600 nm.

FIG. 2 is a correlation diagram showing the relationship between the leakage current density and the electric field strength of the capacitance of the first embodiment of the present invention and the conventional product.

The leakage current density was measured after performing a heat treatment at 1000°C after electrode formation. Further, the electric field strength indicates the electric field strength applied to the Ta209 layer 2.

As shown in FIG. 2, the titanium nitride layer 3 is
0. By inserting the polycrystalline silicon layer between the layer 2 and the polycrystalline silicon layer 4, leakage current can be significantly reduced by several orders of magnitude. This is the following reaction between polycrystalline silicon and Ta2o5: 13Si + 2Ta20g-+ 4TaSi2Mo5S
This is because the titanium nitride layer effectively prevents i02. This suppresses the occurrence of pinholes and weak spots in the T'a205 layer 2, which is a capacitive film, and suppresses an increase in leakage current of the capacitive film, deterioration of dielectric strength, and a decrease in reliability.

FIG. 3 is a sectional view of a second embodiment of the invention.

Similar to the first embodiment, a Ta205 layer 2 is formed on a silicon substrate 1.
is deposited to a thickness of 5 to 30 nm, and then a titanium nitride layer 3 is deposited to a thickness of 30 to 20 Or+m.

Next, a titanium layer of 100~
Deposit to a thickness of 600 nm. Next, the titanium layer 5 is etched using photolithography to form electrodes. After removing the photoresist, the titanium layer 5 may be heat-treated by lamp annealing or the like to form a titanium nitride layer 6 around the titanium layer 5.

In this example, the electrodes are a titanium layer 5 and a titanium nitride layer 3.6.
It consists of. By surrounding the titanium layer 5 with the titanium nitride layer 3.6, a reaction between the titanium layer 5 and the Ta205 layer 2 can be prevented, and a reaction between the titanium layer 5 and the interlayer film can also be prevented. As a result, even if heat treatment is performed after forming the electrodes of the capacitor part, a capacitor can be formed without increasing the leakage current of the capacitor film or deteriorating the dielectric strength.

In this example, the titanium nitride layer 3 as a metal nitride layer between the titanium layer 5 and the Ta205 layer 2 and the titanium nitride layer 6 as a metal nitride layer surrounding the titanium layer 5 have the same nitride layer. Although titanium is used, even if these metal nitrides are different, such as titanium nitride and tungsten nitride, the effect is the same as in this embodiment. Other metal nitrides and other conductor layers may be freely combined, and the effect remains the same.

In addition, in the first and second embodiments of the present invention, the present invention was explained using a capacitor on a silicon substrate, but the present invention can also be applied to a capacitor on an electrode made of polycrystalline silicon, silicide, high melting point metal, etc. Even if you use , the effect is the same. Ta on the capacitive film
Using a metal oxide other than 205, a film in which silicon or other metal is mixed in the metal oxide, or a capacitive film with a multilayer structure consisting of a silicon oxide film, a silicon oxide film, a silicon nitride film, and a metal oxide. However, the effect is the same.

The combination of the conductor layer of the electrode on the capacitor film, the metal nitride between the conductor layer and the capacitor film, and the metal nitride surrounding the part of the periphery of the conductor layer that is not in contact with the capacitor film is free. The effect is the same as in this embodiment.Furthermore, the electrode on the capacitive film may be formed only of metal nitride.

〔Effect of the invention〕

As explained above, in the present invention, by sandwiching a chemically stable metal nitride with low specific resistance between the electrode of the capacitive part and the capacitive film, the capacitive film and the electrode can be bonded by heat treatment after electrode formation. This has the effect of suppressing reactions and obtaining excellent capacitance without increasing leakage current or deteriorating dielectric strength of the capacitive film.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the first embodiment of the present invention, and FIG. 2 is a sectional view of the first embodiment of the present invention.
FIG. 3 is a sectional view of the second embodiment of the present invention. 1... Silicon substrate, 2... Ta205 layer, 3...
・Titanium nitride layer, 4... Polycrystalline silicon layer, 5...
Titanium layer, 6...Titanium nitride layer.

Claims (1)

[Claims] a first electrode made of a semiconductor layer or a conductor layer formed on a substrate; a dielectric layer made of a metal oxide having a valve action provided on the first electrode; and a metal nitride or a metal. A capacitor section comprising an insulating layer made of an oxide layer and covering the dielectric layer, and a second electrode provided on the insulating film opposite to the first electrode. semiconductor device.