JP2000031387A - Manufacture of dielectric thin film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a small-sized dielectric thin film capacitor having large capacitance and a high breakdown voltage. SOLUTION: A titanium film 12 deposited by a sputtering method, and a lower part electrode composed of a platinum film 13 are formed on a silicon substrate 11. The surface of the electrode is roughened by a method like mechanical polishing. On the roughened surface, a dielectric film 14 of an ATO film formed by alternately laminating alumina and titania by an atomic layer epitaxy method is deposited. By depositing again a platinum film 15, an upper part electrode is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a dielectric thin film capacitor using a dielectric thin film having a high dielectric constant.

[0002]

2. Description of the Related Art With the development of integrated circuits, the miniaturization of electronic circuits has been more and more advanced. Along with this, miniaturization of capacitors, which are essential circuit elements for various circuits, has become even more important. As a conventional thin film capacitor, for example, as disclosed in JP-A-63-49385, a dielectric such as silicon oxide (SiO ₂ ) or tantalum oxide (Ta ₂ O ₅ ) is used. It is common to use a material having a dielectric constant of at most 20. In recent years, in order to increase the capacity of a capacitor, titanium oxide (hereinafter referred to as TiO ₂ ) or lead zirconium titanate (Pb (Zr _0.5 Ti
_0.5 ) O ₃ (hereinafter abbreviated as PZT), lead magnesium niobate (Pb (Mg _0.5 Nb _0.5 ) O ₃ , hereinafter PMN
, Etc.) are being studied.

[0003]

When a thin film capacitor is manufactured, in order to increase the capacitance, the electrode area is increased, the thickness of the dielectric film is reduced, or a dielectric having a large relative permittivity is used. There are three methods. However, when the electrode area is increased, the area occupied by the capacitor increases.

[0004] When the thickness of the dielectric film is reduced, the probability of a short circuit between the electrodes due to a defect in the dielectric increases, and the yield of the thin film capacitor decreases. There was a problem. TiO ₂ , PZT, and PMN, which are materials having a large relative dielectric constant, have a problem of low withstand voltage and a problem of a manufacturing method, and their practical use has not progressed much.

In view of such circumstances, an object of the present invention is to provide a method of manufacturing a dielectric thin film capacitor having a small size, a large capacity, and a high withstand voltage.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of manufacturing a thin film capacitor in which a lower electrode, a dielectric thin film and an upper electrode are formed on a substrate. Is heated by heating the substrate, a reactive gas is flowed over the lower electrode, and a thermal thin film is formed by using a surface reaction to form a dielectric thin film.

The surface area of the electrode can be increased by roughening the lower electrode, and by using a thermal CVD method utilizing a surface reaction by heating the substrate as a method of manufacturing a dielectric thin film, the surface of the substrate having irregularities can be formed. However, a uniform film thickness can be obtained.
As a method of roughening the lower electrode, any of mechanical polishing using a wrapping film, a vacuum deposition method of a lower electrode material, and chemical etching is used.

[0008] Mechanical polishing using a wrapping film is the easiest surface roughening method, and vacuum evaporation and chemical etching are methods suitable for large-area and mass production. As thermal CVD, atomic layer epitaxy, MO
One of the CVD methods. Either way,
A uniform film thickness can be obtained even on an uneven substrate, a withstand voltage can be secured, and a short circuit between electrodes can be prevented.

Preferably, the dielectric thin film is a composite film in which alumina and titania are alternately laminated. Alumina has a relatively low relative dielectric constant but a high withstand voltage, and titania has a high relative dielectric constant but a low withstand voltage. By using both layers, a capacitor having a large relative dielectric constant and a high withstand voltage can be realized.

[0010]

FIG. 1 is a schematic sectional view of a dielectric thin film capacitor according to a first embodiment of the present invention. 11 is a silicon wafer with a thermal oxide film used as a substrate, 12 and 13 each have a thickness of 20 nm,
A 00 nm titanium (Ti) film and a platinum (Pt) film.
Reference numeral 14 denotes a dielectric thin film of a composite film (hereinafter, referred to as an ATO film) in which Al ₂ O ₃ and TiO ₂ are alternately stacked, and 15 denotes a thickness of 2
The upper electrode is made of Pt of 00 nm.

Hereinafter, the manufacturing method will be described. A silicon wafer is thermally oxidized to form a thermal oxide film 11a having a thickness of 0.5 μm. Next, in each case, Ti is used by RF magnetron sputtering.
A film 12 and a Pt film 13 are deposited. Subsequently, the lower electrode is roughened using a wrapping film. The film used was an ultraprecision wrapping film (for example, # 20000 manufactured by Sumitomo 3M), and the surface roughness after roughening was about 5
0 nm.

Thereafter, a total of five layers of Al ₂ O ₃ and TiO ₂ each having a thickness of 4 nm are alternately laminated by atomic layer epitaxy (ALE) to form a dielectric thin film 14 having a thickness of 20 nm. As a raw material, aluminum trichloride (AlCl ₃ ), titanium tetrachloride (TiCl ₄ ), and pure water (H ₂ O) are used, and deposited at a substrate temperature of 500 ° C. and a pressure of 0.4 Pa.
Solid AlCl ₃ is heated and evaporated, and liquid TiCl ₄ and H ₂ O are transported by bubbling with argon (Ar). The deposition rate is about 0.1 nm / sec.

A Pt film 15 is formed thereon by RF magnetron sputtering as an upper electrode. Electrode diameter 2mm
, And the capacitance was measured at a frequency of 1 MHz, and compared with a capacitor in which the lower electrode was not roughened (Comparative Example 1). As a result, the capacitance was 40 nF. No short circuit occurred between the electrodes, and the breakdown voltage was 10 V or more. Since the rated voltage in use is about 3 V, a withstand voltage of 10 V or more is sufficient.

Since the capacitance of Comparative Example 1 was 28 nF, the relative dielectric constant was about 20. The increase in capacity of about 40% from Comparative Example 1 is an effect of roughening the electrode surface. It is considered that since the dielectric film was formed by the thermal CVD method, the film was dense and uniform even though the thickness was small, so that no short circuit between the electrodes occurred.

Embodiment 2 FIG. 2 is a simulated sectional view of a thin film capacitor according to a second embodiment of the present invention.
Reference numeral 21 denotes a silicon wafer with a thermal oxide film used as a substrate. Reference numeral 22 denotes a 20 nm-thick Ti film formed by an RF magnetron sputtering method. Reference numeral 23 denotes zinc oxide (ZnO), which is a conductive material formed by an electron beam evaporation method. The film formation temperature was 300 ° C., and the film thickness was 500 nm. The surface roughness is about 30 nm, which results in a roughened lower electrode surface.
Reference numeral 24 denotes a composite film of alumina and titania (ATO) formed by atomic layer epitaxy under the same conditions as in Example 1.
Membrane). Reference numeral 25 denotes a Pt film having a thickness of 200 nm formed by an RF magnetron sputtering method.

As in Example 1, evaluation was made under the conditions of an electrode diameter of 2 mm and a frequency of 1 MHz. As a result, it was about 36 nF. No short circuit occurred between the electrodes, and the breakdown voltage was 10 V or more. Since the capacitance of the comparative example in which the lower electrode surface was not roughened was 28 nF, the capacitance was increased by about 30% in this example. This example also means that the capacitance is increased by roughening the surface of the lower electrode, and the withstand voltage is secured by using the thermal CVD method.

Embodiment 3 FIG. 3 is a simulated sectional view of a thin film capacitor according to a third embodiment of the present invention.
31 is a silicon wafer with a thermal oxide film used as a substrate. This wafer was patterned by a wet process to provide irregularities and used as a substrate. The concavo-convex pattern used this time was a forward tapered pattern having a line / space of 1.5 μm and an aspect ratio of 1. On top of this, RF
The thickness of each is 20 nm and 2 by magnetron sputtering.
A 00 nm Ti film 32 and a Pt film 33 were formed to form a lower electrode. Numeral 34 denotes an SrTiO ₃ film formed as a dielectric film 34 by using the MOCVD method. Sr as Sr raw material
(THD) ₂ , TiO (THD) ₂ , N as Ti raw material
_{Using 2} O gas, substrate temperature: 420 ° C, film formation pressure: 13
An SrTiO ₃ film having a thickness of 100 nm was formed at 00 Pa. In addition, THD is 2,2,6,6 tetramethyl-3,
Abbreviation for 5 heptanedione. After film formation by MOCVD method,
A heat treatment at 600 ° C. was performed in an oxygen atmosphere for crystallization.
Reference numeral 35 denotes a 200 nm thick Pt film formed on the dielectric film 34 by the RF magnetron sputtering method, and serves as an upper electrode.

The prepared thin film capacitor was evaluated under the conditions of an electrode diameter of 2 mm and a frequency of 1 MHz in the same manner as in Example 1, and compared with a thin film capacitor using a substrate having no unevenness (Comparative Example 2). As a result, the capacitance increased from 28 nF in Comparative Example 2 to approximately 60 nF in this example, which was approximately doubled. The withstand voltage was 10 V or more. The relative permittivity corresponds to about 100.

As described above, the substrate is formed by the wet process.
It is also possible to roughen the lower electrode by making the surface uneven
It is. As the dielectric material, the above-mentioned ATO film, SrT
iO_ThreeNot only film but Pb (Sc _0.5Ta_0.5) O_Three(P
ST), (Ba_0.5Sr_0.5) TiO_Three(BST), T
a_TwoO_FiveVarious materials are applicable.

[0020]

As described above, according to the manufacturing method of the present invention, in a method of manufacturing a thin film capacitor in which a lower electrode, a dielectric thin film and an upper electrode are formed on a substrate, the lower electrode is roughened. Then, by forming a dielectric thin film by a thermal CVD method utilizing a surface reaction due to substrate heating, a small and large-capacity dielectric thin film capacitor can be realized.

The present invention satisfies the demand for miniaturization and weight reduction of a small power supply and a capacitor incorporated in an IC circuit or the like, and greatly contributes to miniaturization of electric equipment, particularly portable equipment.

[Brief description of the drawings]

FIG. 1 is a simulated cross-sectional view of a dielectric thin film capacitor according to a first embodiment of the present invention.

FIG. 2 is a simulated cross-sectional view of a dielectric thin film capacitor according to a second embodiment of the present invention.

FIG. 3 is a simulated sectional view of a dielectric thin film capacitor according to a third embodiment of the present invention.

[Explanation of symbols]

 11, 21, 31 Substrate 12, 22, 32 Ti film 13, 33 Pt film 14, 24, 34 Dielectric film 15, 25, 35 Pt film 23 ZnO film

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yukinori Kawamura 1-1-1, Tanabe-shinda, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term within Fuji Electric Co., Ltd. 5E082 AB03 BC39 EE05 EE15 EE18 EE19 EE23 EE37 EE42 FF15 FG03 FG19 FG26 FG27 FG41 FG58 KK01 MM24 5F038 AC05 AC10 AC15 AC16 AC17 AC18 EZ20 5F058 BA11 BD02 BD05 BF06 BJ10

Claims (6)

[Claims] In a method of manufacturing a dielectric thin film capacitor in which a lower electrode, a dielectric thin film and an upper electrode are formed on a substrate, a substrate having a roughened lower electrode is heated and the lower electrode is placed on the lower electrode. A method of manufacturing a dielectric thin film capacitor, which comprises flowing a reaction gas and forming a dielectric thin film using a surface reaction by a thermal CVD method. 2. The method according to claim 1, wherein the step of roughening the lower electrode is mechanical polishing using a wrapping film.
A method for producing the dielectric thin film capacitor according to the above. 3. The method for manufacturing a dielectric thin film capacitor according to claim 1, wherein the step of roughening the lower electrode is a vacuum deposition method of a lower electrode material. 4. The method according to claim 1, wherein the step of roughening the lower electrode is a chemical etching. 5. The method according to claim 1, wherein the thermal CVD method is an atomic layer epitaxy method. 6. The method according to claim 5, wherein the dielectric thin film is a composite film in which alumina and titania are alternately laminated.