JPS6130018A - Thick film capacitor and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a thin film capacitor and a method for manufacturing the same, and more particularly to a thin film capacitor whose main constituent material is Ta110g, which has a high dielectric constant, and particularly an integrated circuit whose main constituent material is St. The present invention relates to a thin film capacitor having a high capacitance per unit area and suitable for use as a capacitive element in the field, and a method for manufacturing the same.

[Background of the invention]

11 film capacitors formed on semiconductor substrates such as SI play an important role as storage capacitors in semiconductor devices such as high-sensitivity memory integrated circuits and display active matrix drive circuits. In particular, as the degree of integration of circuits increases, the area occupied by storage capacitors is becoming impossible to ignore, and in order to reduce the area occupied, there is a need for thin film capacitors with high capacitance per unit area. 6 is increasing.

Hitherto, SiOg formed by a thermal oxidation method or a CVD method has been used as an insulating layer material for thin film capacitors applied to these semiconductor devices. Since 5i02 has a low dielectric constant of 3.4, its use has the disadvantage that the capacitance per unit area does not increase.

In order to improve this drawback, attempts have been made to increase the capacitance by reducing the thickness of the SiOt film, but in this case, it is said that the dielectric strength of the thin film capacitor decreases as the thickness of the SiOt film decreases. produce defects.

In order to overcome the above-mentioned problems, by using a material with a high dielectric constant (relative permittivity: 25) such as Tag Os as the insulating layer material of a thin film capacitor, it is possible to create a thin film capacitor with a high capacitance per unit area. Attempts have been made to obtain Tag O5 can be formed by a method such as a vapor phase growth method or thermal oxidation or anodic oxidation of a previously formed Ta film.

However, Tag 05 formed by this method
Thin film capacitors using TaQks have the disadvantage of large leakage current due to the presence of many capture levels in the TaQks.

In addition, Tall0s formed by CVD method, thermal oxidation method, etc.
However, since a significant increase in leakage current is observed even with heat treatment at temperatures of about 200°C, the problem is that it does not show resistance to heat treatment at 400 to 500°C, which is used in normal semiconductor device fabrication processes, and cannot be applied to semiconductor devices. There is a point.

On the other hand, Ta formed on Si by sputtering method
Thin film capacitors mainly composed of 2O5 have low leakage current and exhibit sufficient resistance to heat treatment, but St.
Since a transition region with a low dielectric constant exists at the interface with Ta90s and Ta90s, there is a drawback that the dielectric constant of the insulating layer becomes low.

[Summary of the invention]

The present invention has been made in view of the above points, and aims to provide a thin film capacitor whose main constituent material is Ta2O5 formed by sputtering on a Si substrate and which has a large capacitance per unit area, and a method for manufacturing the same. purpose.

Therefore, the thin film capacitor according to the present invention forms a dielectric thin film mainly composed of TaQ05 on a Si substrate,
A thin film capacitor in which an electrode layer is further formed on the dielectric *m is characterized in that the crystal orientation of the 31 substrate in contact with the dielectric thin film mainly composed of Ta@05 is (110). It is something to do.

In addition, the method for manufacturing a thin film capacitor according to the present invention uses Ta or T as a target in an inert gas atmosphere containing oxygen, and sputters the film onto a Si single crystal with a crystal orientation of (110). This method is characterized by forming a dielectric thin film whose main constituent is Ta2Og.

According to the present invention, Ta2 is deposited on Si with crystal orientation (110).
By forming O5, it is possible to reduce the thickness of the low dielectric constant transition layer formed at the interface between the Si substrate and Ta2O5, making it suitable for capacitive elements in integrated circuits and increasing the capacitance per unit area. It is possible to obtain a thin film capacitor with large leakage current and low leakage current.

Furthermore, the method for manufacturing a thin film capacitor according to the present invention has the advantage that the above-mentioned thin film capacitor can be easily manufactured.

[Detailed description of the invention]

The present invention will be explained in further detail.

FIG. 1 is a cross-sectional view of one embodiment of a thin film capacitor according to the present invention, in which 1 is a Si substrate, 2 and 3 are Tag O
5 as the main constituent material (a thin dielectric layer,
In this insulating layer (dielectric thin layer), 2 is a low dielectric constant interfacial transition layer, 3 is a high dielectric constant uniform layer, and 4 is A
! It is an electrode.

As is clear from FIG. 1, this thin film capacitor has a low dielectric constant interfacial transition layer 2 whose main constituent is Ta2Og and a high dielectric constant uniform layer 3 laminated in sequence on a Si substrate 1. , on this uniform layer 3 and on the Si substrate 1
A β electrode 4 is formed on the back surface of each.

As mentioned above, the Si substrate 1 in contact with the low dielectric constant interfacial transition layer 2 mainly composed of Ta2O5 has a crystal orientation of (
110), and as is clear from the description below and FIGS. 2 and 3, the crystal orientation of the St single crystal in contact with the dielectric thin film 2 whose main component is Ta2O5 is (110).
10), the low dielectric constant interfacial transition layer 2
It becomes possible to thin (thin).

To manufacture such a thin film capacitor, first, Ta'2O5 is mainly sputtered by magnetron sputtering using a Ta or Ta2O5 sintered body as a target on a Si substrate and using an oxygen-containing inert gas as the sputtering gas. Form an insulating layer as a constituent material. The sputtering method used here generates a discharge in a low vacuum, ionizes the sputtering gas, accelerates the ions with an electric field, and causes them to collide with the target, causing constituent atoms to be repelled from the target and deposited on the substrate. In particular, magnetron sputtering is a technique in which a magnetic field is applied at the same time so that discharge occurs under a lower pressure than in general sputtering.

In the present invention, by using an inert gas containing oxygen as a sputtering gas, oxygen ions are generated during discharge, and T
This prevents deviation from the stoichiometric composition of at06. T
In the initial process of a10g formation, an interfacial transition layer is formed by the reaction between the Si surface, atoms constituting the target, and ion species in the sputtering gas. Since this interfacial transition layer is composed of tantalum, silicon, and oxygen, the dielectric constant is T
Although it is lower than a2O g, after the interfacial transition layer is formed, si
Because the reaction on the back surface does not proceed, Tag O with a high dielectric constant
Only 5 is deposited. As a result, the insulating layer is composed of two layers: a low dielectric constant interfacial transition layer and a high dielectric constant Ta2O5 layer, and the dielectric constant of the insulating layer is higher than that of Si02.

After forming such an insulating layer, an AJ electrode is deposited on the high dielectric constant uniform layer and the Si substrate to form a thin film capacitor.

In the following, in the present invention, it will be quantitatively and concretely explained how the Si crystal orientation of the St layer in contact with the layer whose main constituent material is Ta2O5 is (110'').

Figures 2 and 3 show that the crystal orientations are (100) and (
110) shows the dielectric constant distribution in the film when Ta2O5 is formed on the Si substrate.

As is clear from these figures, S of any crystal orientation
It is understood that even on the i-substrate, Ta2O6 consists of a low dielectric constant interfacial transition layer and a high dielectric constant uniform layer.

The dielectric constant of the uniform layer is 25, and no change due to the crystal orientation of the substrate is observed.

On the other hand, the thickness of the low dielectric constant region is 130 on the (100) plane and 85 on the (110) plane. Such changes are caused by the interfacial transition layer forming a sputtered particle with the Si surface.
Since it is formed by reaction with ion species in the sputtering gas, the formation of the interfacial transition layer is a result of being influenced by the crystal orientation of the Si substrate.

From the above experimental results, the dielectric constant of the entire insulating layer is higher when using a Si substrate with a crystal orientation of (110) than when using a Si substrate with a crystal orientation of (100). Large capacitance l! You can see that the membrane capacitor can be replaced.

Examples will be described below.

Using single-crystal Si (p-type, surface index (110), resistivity 0.07 to 0.13 ohis-cs+) as an example substrate, a Ta2O5 sintered body (purity 99.99%) was used as a target, and oxygen was % mixed argon gas atmosphere, an insulating layer mainly composed of Ta2O5 was formed by magnetron sputtering. Following the formation of the insulating layer, an ^i electrode was formed and heat treated at 450° C. in a hydrogen atmosphere.

FIG. 4 shows the dependence of the dielectric constant of the thin film capacitor thus formed on the thickness of the insulating layer. At the same time, as a comparative example, p
Type, surface index (100), specific resistance 0.07~0.13o
hm, elm and 10~2Oob+w, cm
The results are shown when using single crystal St. In the figure, the opening is a graph of the thickness dependence of the insulating material layer according to the embodiment of the present invention, and △ is the surface index (100), 0.07 to 0.13o.
ha+, am Si crystal, ○ is surface index (100)
, 10-2 Ooha+, cm is a graph when using a Si crystal.

As is clear from this figure, the dielectric constant of the entire insulating material layer shows a tendency to increase uniformly as the film thickness increases.

As shown in FIGS. 2 and 3, the dielectric constant of the entire insulating layer is higher on the (110) plane than on the (100) plane because the thickness of the low dielectric constant region is smaller. At a film thickness of 800 mm, the dielectric constant of the insulating layer on the (110) plane is 21, and (
The value was about 20% higher than that on the 100) surface.

In the above example, argon gas mixed with 10% oxygen was used as the sputtering gas, but the oxygen content was 5 to 70%.
The same effect can be obtained by changing it within the range of . Also,
Although a Ta2Gg sintered body was used as the target, a similar thin film capacitor can be obtained using Ta.

Example 2 Single crystal Si (p type, surface index (100”) specific resistance, 1
2 to 1.8 ohm-am) A V-groove was formed on the substrate using photolithography. Surface index (100
) By forming a V-groove having an angle of 45 degrees with respect to the substrate surface, the surface of the V-groove can be set to (110).

An insulating material layer 1000 is formed on this V-groove in the same manner as in Example 1.
The electrode was formed followed by the deposition of the AN electrode.

The cross-sectional structure is shown in FIG. In FIG. 5, 5 is a Si substrate, 6 is an insulating material layer, and 7 is an A4 electrode.

■The dielectric constant of the insulating material layer 6 formed on the groove is that the V-groove surface is (
110), the value was ~7 times higher than that of SiOt.

〔Effect of the invention〕

As explained above, according to the thin film capacitor of the present invention, by forming Ta*05 on St with crystal orientation (110), a low dielectric constant transition layer is formed at the interface between Si and Ta@05. It becomes possible to reduce the thickness of
It is possible to obtain a thin film capacitor that is suitable for a capacitive element in an integrated circuit, has a large capacitance per unit area, and has a low leakage current.

Furthermore, the method for manufacturing a thin film capacitor according to the present invention has the advantage that the above-mentioned thin film capacitor can be easily manufactured.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a thin film capacitor according to the present invention, FIG. 2 is a distribution in the film thickness direction of the dielectric constant of an insulating layer formed on the St (100) plane, and FIG. Figure 4 is a graph showing the film thickness dependence of the insulating layer formed on the St (100) plane and the Si (110) plane; The figure is a sectional view of another embodiment of the thin film capacitor according to the present invention. 1.5...Si substrate, 2...Interfacial transition layer, 3
・・・Horizontal layer, 4.7 ・・・AJ electrode, 6 ・・・
insulation layer.

Claims (2)

[Claims] (1) A thin film capacitor in which a dielectric thin film containing Ta_2O_5 as a main component is formed on a Si substrate, and an electrode layer is further formed on this dielectric thin film.
A thin film capacitor characterized in that a Si substrate in contact with a dielectric thin film mainly composed of O_5 has a (110) crystal orientation. (2) Ta or T in an inert gas atmosphere containing oxygen
A method for manufacturing a thin film capacitor, which comprises using a_2O_5 as a target and forming an insulating layer containing Ta_2O_5 as a main component on a Si single crystal with a crystal orientation (110) by a sputtering method.