JPS62118559A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent silicide reaction between a metal oxide film such as a Ta2O5 film used in a capacitor part and a silicon substrate, to prevent reaction between the metal oxide such as Ta2O5 film and a polycrystalline silicon electrode located on the metal oxide film such as the Ta2O5 film, to reduce leaking currents and to prevent reduction in capacitance due to heat treatment, by providing a silicon nitride film. CONSTITUTION:A silicon nitride film 102 formed on the surface of a silicon substrate 101 is used to prevent silicide reaction between a Ta2O5 film and the silicon substrate when the Ta2O5 film is formed in the succeeding process. The diffusion coefficient of oxygen in the silicon substrate 101 is not oxidized through said Ta2O5, and the capacitance is not reduced. A silicon nitride film 104, which is formed on high dielectric-constant material, is formed by, e.g., a pressure reduced CVD method. Then, the silicon nitride film is thermally oxidized and a thin silicon oxide film 105 is formed. The best advantage of this oxidation is the fact that the basis film is grown by the oxidation of the surface of the silicon substrate 101 through pinholes in the Ta2O5 film 103 and the silicon nitride film 102.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to the structure of an information storage capacitor used in a dynamic RAM or the like.

[Conventional technology]

Integrated circuits formed on semiconductor substrates, particularly silicon semiconductor substrates, are becoming increasingly highly integrated and have a large capacity, and the degree of integration of integrated circuits such as memory devices is increasing to 1 Mbit or more.

Currently, in IC memories such as dynamic RAM (hereinafter referred to as DRAM), information storage units (hereinafter referred to as cells)
It is considered most suitable for miniaturization to consist of one transistor and one information storage capacitor. In this information storage method, the area of the information storage capacitor portion of the cell occupies most of the semiconductor chip. In this type of device, the chip size must be made as small as possible from the viewpoint of yield and cost. Therefore, the most effective means for increasing the capacity of DR and AM using this method is to reduce the area of the information storage capacity section.

However, this information storage capacity requires a capacity of 50 fF or more to ensure reliability against malfunctions caused by errors caused by alpha rays. It is not allowed to make it smaller. Therefore, due to the reduction in the size of the information collection section, the dielectric film has become thinner.
A method is taken to ensure that the answer is 10′#i. However, for example, if a conventional silicon oxide film with a specific electrical charge ratio of 3.9 is applied to a megabit class D It AM, the film thickness of the silicon oxide film is less than Vi1oo8,
The dielectric strength of such a thin film cannot meet the requirements for power supply (5), and it is predicted that it will be impossible to use it. Against this background, a structure has been proposed in which a groove is dug in the substrate surface and the sidewalls of the groove are used as a capacitive part as a means of effectively ensuring a large die capacity plate part σ11)* with a thick oxide film. However, even if this structure is used, for example, in a 4 to 16 megabit class DRAM, the depth of the groove is 1. Q 7zm, and there remain problems such as difficulty in forming a 1JL pole in the subsequent process. Therefore, the same
In order to increase the storage capacity of Kamibake Ffti Dan, the use of a high dielectric constant material for the insulator and 1~ is being considered, and if this is used, the groove depth of the groove capacitance can also be made shallow. It is expected that the process for manufacturing the device will become easier and that it will become possible to form even finer elements.

Recently, Ta205 has been particularly used as such a high dielectric constant material.
Attempts have been made to apply this to information storage capacitors, but the current situation is that the leakage current is large and the characteristics for practical use have not been achieved.

[Problems to be Solved by the Invention] Conventionally, the cause of large leakage current in a storage capacitor using a material with a high current visiting rate, for example, Ta2O5, is that the material used as the insulating film of the information storage capacitor (hereinafter abbreviated as capacitor) This is presumed to be due to the fact that the Ta205 film that was used is likely to cause a silicide reaction with the Si substrate, and also with the polycrystalline silicon electrode formed as a counter electrode with the substrate, resulting in a significant decrease in insulation properties. In other words, the inventor presumes that the Tag 05 film undergoes a heat treatment process, causing a solid phase reaction with the polycrystalline silicon electrode or the Si substrate, or that the Ta2O5 film becomes polycrystalline, resulting in poor insulation properties. ing. Furthermore, the Ta205 film has the disadvantage that during the thermal oxidation process after the Ta205 film is formed, oxygen easily diffuses into the Ta205 film, so that the surface of the silicon substrate is oxidized and the capacitance value of the capacitive part is reduced.

The purpose of the present invention is to 'prevent the silicide reaction between the metal oxide film such as the Ta205 film used in the BitA part and the silicon substrate,' and ['to prevent the silicide reaction between the metal oxide film such as the Ta205 film and the Ta! It prevents reaction with the polycrystalline silicon electrode located on the top of the metal oxide film such as O, film, etc., reduces leakage current, and further improves the Ta20B
An object of the present invention is to provide a semiconductor device having an information storage capacity that prevents a decrease in capacity due to heat treatment after forming a metal oxide film such as a film.

[Means for solving problems]

The semiconductor device of the present invention includes an electrode provided on a semiconductor substrate or an insulator substrate, a silicon nitride film on the electrode, and a Ta1
05, '1''iol, Nb206, HaT
an insulating layer in which a metal oxide film of i03, a silicon nitride film, and a silicon oxide film are sequentially formed;
and an electrode provided on the insulating layer.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

In FIG. 1, 101 is a silicon substrate on which a device is formed. The silicon substrate may be a substrate having either P-type or n-type conductivity.

102 is a silicon nitride film formed on the surface of the silicon substrate 101. The silicon nitride film can be formed by a direct thermal nitriding method for nitriding a Si substrate, a plasma direct thermal nitriding method, a chemical vapor deposition method (CVD method), etc., and is preferably formed to a thickness of about 30 to 50 A.

This silicon nitride film is for preventing a silicide reaction between the Ta205 film and the silicon substrate when forming the Ta20B film in a later step. Furthermore, this silicon nitride film has a small diffusion coefficient of oxygen in the film, so Ta
During the thermal oxidation treatment step after forming the Ta205 film, the Ta205
It also has the effect of preventing the surface of the silicon substrate 1010 from being oxidized through the film and reducing the capacitance. 103 is Ta205, which is a high dielectric material. Ta205 is formed by thermally oxidizing metal Ta by sputtering or other methods, or by high-frequency sputtering or chemical vapor deposition (CV).
It can be formed by a method such as directly forming 1'az05 by method D). Titanium (Ti) is used as a high dielectric constant material.
Other oxides such as zirconium (Zr) and complex oxides such as a'lr03 can be freely selected, and the purpose of the present invention can be achieved. The 6 silicon nitride film, which is a silicon nitride film formed on the 8 electric conductivity material, is formed by, for example, a low pressure CVD method.Next, this silicon nitride film is thermally oxidized. - Form a thin silicon oxide film 105.Silicon nitride film (1) Because the diffusion coefficient of oxygen in the film is small, only a small oxide film of the solder is formed. If there are pinholes in the silicon nitride film, the Ta205 film 1 is removed by thermal oxidation.
03 and silicon nitride film 102 to fill pinholes in the insulating film. Therefore, a capacitor having extremely excellent breakdown voltage characteristics can be realized.

Furthermore, since the silicon nitride film itself is hardly oxidized, the capacitance does not decrease. 106 is a polycrystalline silicon electrode that serves as a counter electrode to the silicon substrate.1 This electrode is made of a polycrystalline silicon layer and silicon.The capacitor formed using the present invention has a current density when a voltage of 7V is applied to the electrode. IOA/cm” compared to Ta205 single layer film.
Leakage current can be reduced by more than 3 orders of magnitude, and '1. 'a205
Even after heat treatment after film formation, a capacitance value that is almost the same as the capacitance value estimated from the film thickness of each layer forming the capacitor is obtained.

FIG. 2 is a longitudinal sectional view of another embodiment of the present invention, in which the capacitance formation method is applied to the groove structure. The film forming method is the same as the method explained in FIG.
3 is preferably formed by CVD method. Also, 10
If electrode 6 is formed from polycrystalline silicon by CVD method,
Electrodes can be embedded extremely easily inside the groove. According to this embodiment, it is possible to increase the capacitance value, and as with the embodiment shown in FIG. 1, it is possible to obtain a capacitance in accordance with the designed value with significantly reduced leakage current.

In the above embodiment, the capacitor was formed on the Si substrate, but the capacitor was formed on the other electrode H (4) k''-. There are no restrictions such as examples.

Further, although polycrystalline silicon is used for the upper electrode, the present invention is not limited to this; metals such as A, L, W, and Mo may also be used.

〔Effect of the invention〕

As explained above, the present invention utilizes Ta2O, which is a high dielectric material.
By providing a silicon nitride film between a metal oxide film such as an S film and a silicon substrate, it is possible to prevent a reaction between a metal oxide film such as a Ta206 film and a silicon substrate. It also has the effect of suppressing oxidation of the silicon substrate surface due to thermal oxidation treatment after forming a metal oxide film such as a Ta205 film. Also'
By providing a silicon nitride film between a metal oxide film such as a l'a20s film and a polycrystalline Jil silicon electrode,
It also has the effect of preventing reactions between metal oxide films such as the 205 film and polycrystalline silicon electrodes. Furthermore, the silicon nitride film contains Na
9 because it has a large diffusion suppressing effect on impurities such as
The capacitor according to the present invention also has excellent electrical stability.

As described above, by using the structure of the present invention, it becomes possible to take advantage of the properties of high dielectric constant materials, and it is possible to form an information storage capacitor section that has a large capacitance per unit area and a small leakage current.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the invention, and FIG. 2 is a longitudinal sectional view of another embodiment of the invention. 101゛...°°゛Silicon J[,102...
Silicon nitride film, 103...'], 'a205 film, 104... Silicon nitride film, 105...
...Silicon oxide film, 106...Polycrystalline silicon electrode. $ l Illustration 2 Illustration procedure amendment (voluntary) 1. Indication of incident 1985 Percentage request No. 258
867 No. 2, Title of invention: Semiconductor device 3, Relationship with the amended person's case Application: Daito [Shiba, Toshiro-ku/i I-1133-1-shi] (423) NEC Corporation Representative Tadahiro Sekimoto 4; Agent TiO8 1137-8, i'21t, Minato-ku, Tokyo]・
Sumitomo Sanda Building 11 Hondenki Co., Ltd. 5, Claims column and Detailed Description of the Invention column 6 of the specification to be amended, content of the amendment (1) n11 of the scope of patent raIIt sought in the specification ? I have made the correction as shown in the attached sheet. 1su〇(2) Specification page 2, 16r, r
141 V'-by] has been amended to ``by line, etc.''. (3) The description on page 5, lines 11 and 12 of the specification "n, ta'[1! pole and the electrode provided on the semiconductor substrate or insulator substrate" is defined as one semiconductor substrate or electrode. ``On the semiconductor substrate or the electrode'':''1. (4) The statement "benthic method" on page 6, line 20 of the specification has been corrected to "growth method." The appended paper's revised claims include: ``A semiconductor substrate or a structured electrode, a silicon nitride film on the semiconductor substrate or on the TFI layer, and Ta205. Completely equipped with an insulating layer formed by sequentially laminating a metal oxide film of TiO2, Nb2O5, Ba'l'i03, a silicon nitride film, and a silicon oxide film, and an electrode provided on the insulating layer. A semiconductor device that is characterized by its capacitance being gold-biased. ”

Claims (1)

[Claims] An electrode provided on a semiconductor substrate or an insulator substrate, a silicon nitride film on the electrode, Ta_2O_5, TiO_2,
Equipped with a capacitor consisting of an insulating layer formed by sequentially laminating a metal oxide film of Nb_2O_5 or BaTiO_3, a silicon nitride film, and a silicon oxide film, and an electrode provided on the insulating layer. A semiconductor device characterized by: