JPH0748448B2 - Thin film capacitor and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film capacitor which occupies a small area and is suitable for high integration, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Electronic circuits have become smaller and smaller in recent years due to the development of integrated circuit technology, and miniaturization of capacitors, which are indispensable circuit elements for various electronic circuits, has become more important. As this capacitor, a thin film capacitor using a dielectric thin film is used by being formed on the same substrate as active elements such as transistors, but with the rapid miniaturization of active elements, downsizing of thin film capacitors Is late,
It has become a major factor that prevents further high integration. This is because the conventionally used dielectric thin film material is S
This is because materials such as iO ₂ and Si ₃ N ₄ which have a dielectric constant of 10 or less are limited, and it is necessary to develop a dielectric thin film having a large dielectric constant as a means for miniaturizing the thin film capacitor. Has become. BaTiO ₃ , SrTi, which is a perovskite type oxide represented by the chemical formula ABO _3.
O ₃ , PbZrO ₃ and ilmenite type oxide LiNb
It is known that oxides belonging to ferroelectrics such as O _{3 and} Bi ₄ Ti ₃ O ₁₂ have the above-mentioned single composition and mutual solid solution composition, and have a dielectric constant of 100 to 10,000 in a single crystal or ceramic. Are widely used in ceramic capacitors. Thinning these materials is extremely effective for miniaturizing the above-mentioned thin film capacitor, and research has been conducted for quite some time. Among them, as an example in which relatively good characteristics are obtained, Proceeding of the Eye Lee Lee
ings of the IEEE), Volume 59, No. 10, 1440-14
There is a paper published on page 47, and a BaTiO ₃ thin film formed by sputtering and heat treated has a dielectric constant of 16 (prepared at room temperature) to 1900 (heat treated at 1200 ° C.).

On the other hand, the electrode material which is widely used in the present highly integrated circuits is a low resistance silicon layer obtained by doping polycrystalline silicon or a part of the silicon substrate itself with a high concentration of impurities. Hereinafter, these are collectively called a silicon electrode. Since a fine processing technology has been established for silicon electrodes and is already widely used, if a good high-dielectric-constant thin film can be formed on silicon electrodes, it can be used for capacitors for integrated circuits. Examples of such conventional technology include, for example, the IBM Journal of Research and Development.
opment), 1969 years, the November, paper on SrTiO ₃ film of Shosai pp. 686-695 or Journal of Vacuum Science and Technology, (Journalof Vacuum Science and Technology) , the first
Vol. 6, No. 2, there is a paper on BaTiO ₃ of Shosai pp 315-318. However, since a high film forming temperature is required to obtain a high dielectric constant as described above, a dielectric thin film such as BaTiO ₃ conventionally formed on a silicon electrode has a thickness of about 100 angstroms of silicon dioxide (Si).
It is reported that a layer equivalent to O ₂ ) is formed at the interface. Since this interface layer has a low dielectric constant, the effective dielectric constant of the high-dielectric-constant thin film formed on silicon was greatly reduced as a result, and the advantage of using a high-dielectric constant material was almost lost. . On the other hand, the applicant of the present invention has found that a refractory metal such as Ta, Ti, or W and P on a silicon electrode.
Japanese Unexamined Patent Publication No. 1-238484 discloses that a decrease in dielectric constant can be prevented by using, as a barrier layer, a laminate of high melting point noble metals such as t and Pd.

[0004]

As described above, in order to obtain a higher dielectric constant, the higher the film forming temperature, the better. However, in the method using Japanese Unexamined Patent Publication No. 1-238484, the heat resistance temperature of the barrier layer is 600 ° C. or less, and it is required to raise the barrier characteristics. The present invention solves such conventional problems and provides a thin film capacitor capable of realizing a large capacitance value in a small area without forming a low dielectric constant layer due to a diffusion reaction between a dielectric and an electrode. The purpose is to do.

[0005]

According to the present invention, a first electrode made of a conductor containing silicon, silicide, or silicon, a second electrode made of Ta containing oxygen, a Pt electrode, and a dielectric are provided on a substrate. A thin film capacitor having a structure in which a body film and an upper electrode are sequentially stacked. In the present invention, it is preferable that the second electrode has an atomic fraction O / Ta of oxygen with respect to tantalum of 1.8 or less. In addition, the manufacturing method is the first method for forming a conductor containing silicon, silicide, or silicon on a substrate.
After the electrode, Ta and Pt are sequentially stacked and formed, a heat treatment is performed in an oxygen atmosphere at a temperature of 450 to 800 ° C. to form a second electrode made of Ta containing oxygen.

[0006]

EXAMPLES Next, examples of the present invention will be described. Example 1 FIG. 1 shows the present invention by MIS (Metal Insulator Semiconducto).
r) An example applied to capacity is shown. First, after the isolation oxide film 2 is grown on the semiconductor substrate 1, the sub-contact 3 is opened and the high-concentration impurity layer (first electrode) 4 is formed. Here, the high-concentration layer is for making ohmic contact and corresponds to the first electrode. In this example, N-type impurities are used, but this may be changed according to the conductivity type of the substrate.
P-type impurities may be used in the P-type substrate. Also, the first
In addition to silicon, the electrode may be a conductor containing silicide or silicon. Next, Ta electrode and Pt
The electrodes 5 are stacked by a sputtering method or the like, and heat treatment is performed in an oxygen atmosphere so that the Ta layer contains oxygen and the second electrode 6 is formed. After that, the Pt electrode 5 and the second electrode 6 are selectively formed on the first electrode 4 by using a photolithography technique or the like. Further, the capacitance film 7 is formed by, for example, a sputtering method or the like, and selectively formed on the Pt electrode 5. Here, as the capacitance film 7, for example, SrTiO ₃ or BaTi is used.
Examples include O ₃ and PZT. After that, a protective interlayer film 8 is laminated, only the upper part of the capacitor film 7 is opened, and an upper electrode 9 is formed by a sputtering method or the like and selectively etched to complete the capacitor element. Through these series of steps, the thickness of the capacitance film and each electrode can be determined by the required capacitance value and the magnitude of the barrier property.

FIG. 2 shows the relationship between the film formation temperature of the capacitance film and the dielectric constant of the capacitance film when the heat treatment temperature in the oxygen atmosphere is changed. As a capacitance film, B with a film thickness of about 100 nm
aTiO ₃ was used. In FIG. 2, a curve a has a heat treatment temperature of 400 ° C. or lower, and a curve b has a heat treatment temperature of 450 ° C.
In the case of ℃ or more and 800 ℃ or less, the heat treatment temperature is 85
When the temperature is 0 ° C. or higher, there are typical relationships between the dielectric constant and the film formation temperature. In the curve a, the dielectric constant of the film increases with the film forming temperature, but it significantly decreases at the film forming temperature of 650 ° C. In the curve b, the permittivity monotonically increases up to the film forming temperature of 800 ° C. Also in the curve c, the dielectric constant monotonically increases with the film forming temperature, but the value is smaller than that in the curve b, and moreover, the dielectric constant tends to approach a certain value in the film forming temperature range of 600 ° C. or higher. Rutherford backscattering spectroscopy (RB
As a result of composition analysis by the S) method, the Ta layer contains almost no oxygen at a heat treatment of 400 ° C. or lower, but 450 ° C. or higher 8
At 00 ° C or lower, the Ta layer, which is the second electrode, has an atomic fraction O / T.
It was found that oxygen was contained at a ratio of a = 1.8 or less. On the other hand, when the heat treatment was 850 ° C. or higher, the amount of oxygen in the second electrode was large, and 2 <O / Ta <2.5. From the above results, the barrier property of the Ta layer against Si is 0 in Ta.
It can be seen that the inclusion of oxygen of <O / Ta <1.8 significantly improves. However, it is considered that when O / Ta> 2, an insulating tantalum pentoxide layer is formed and the effective dielectric constant is lowered.

Embodiment 2 FIG. 3 shows a second embodiment of the present invention. This example is MIM (Me
tal Insulator Metal) This is an example applied to capacitance. First,
A separation oxide film 2 is grown on a semiconductor substrate 1, silicon,
A first electrode 4 made of a conductor containing silicide or silicon is formed. The second electrode 6 made of Ta containing oxygen in at least the portion where the capacitance film is formed on the first electrode 6.
And the Pt electrode 5 are formed. The manufacturing method of the second electrode is the first embodiment.
The heat treatment temperature in oxygen atmosphere is 600 ℃
And Next, the capacitor film 7 is formed and then selectively formed. After the interlayer film 8 is further formed, the upper electrode 9 and the first electrode lead-out wiring 10 are formed to complete the capacitive element. Also in this capacitive element, the same relationship between the dielectric constant and the film forming temperature as the curve b of FIG. 2 in Example 1 was obtained.

[0009]

As described above, according to the present invention, when a dielectric film having a large dielectric constant is used, it is possible to prevent the formation of a low dielectric constant layer due to the diffusion reaction between the dielectric and the electrode. It is possible to realize a capacitance value equal to or greater than that of the above-mentioned capacitive element in a much smaller area, and it is possible to greatly contribute to high integration.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between a film forming temperature and a dielectric constant.

FIG. 3 is a sectional view of another embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Separation Oxide Film 3 Sub-Contact 4 First Electrode 5 Pt Electrode 6 Second Electrode 7 Capacitance Film 8 Interlayer Film 9 Upper Electrode 10 First Electrode Wiring

Claims (2)

[Claims] 1. An atomic fraction of oxygen with respect to tantalum , which comprises a first electrode made of silicon, a silicide, or a conductor containing silicon on a substrate, and Ta containing oxygen.
A second electrode having O / Ta of 1.8 or less, a Pt electrode,
A thin film capacitor having a structure in which a dielectric film and an upper electrode are sequentially stacked. 2. The method of manufacturing a thin film capacitor according to claim 1, wherein a first electrode made of silicon, a silicide, or a conductor containing silicon, Ta and Pt are sequentially laminated on the substrate, and then oxygen is formed. In the atmosphere, 450
T containing oxygen by heat treatment at a temperature of ~ 800 ° C
and the atomic fraction O / Ta of oxygen with respect to tantalum is
A method of manufacturing a thin film capacitor, comprising a step of manufacturing a second electrode having a thickness of 1.8 or less .