JPH1041485A - Semiconductor device and production of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively form an oxide dielectric thin film at a low temperature and to attain the cost down of a capacitor and a semiconductor device using this thin film. SOLUTION: An aqueous solution, which contains a polyacid of metal having a peroxide group, produced by letting a hydrogen peroxide solution act on the metal, metallic carbide or organometallic complex containing at least one kind of elements selected out of tungsten, molybdenum, tantalum, niobium, titanium and zirconium, and an aqueous solution of a salt produced from at least one kind of elements selected out of alkaline earth metals, rare earth metals, lead and bismuth and at least one kind of acid selected out of nitric acid, hydrochloric acid and organic acids or their mixture as needed are applied by spin-coating and heat treatment is conducted in an atmosphere containing steam of partial pressure higher than 1Pa at a temperature lower than 400 deg.C. Thus, since an oxide thin film having a similar crystal structure can be inexpensively formed by heat treatment at much lower temperature is comparison with the conventional method of application, even in the process using a resin or the like of low heat resistance, the dielectric thin film can be formed at low cost. Further, a thin film capacitor or semiconductor device using such a thin film can be produced at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a dielectric thin film made of a heat-treated metal peroxide polyacid. Further, the present invention relates to a method for forming a dielectric thin film made of a metal oxide. In particular, the present invention relates to a method for forming a uniform and high-performance metal oxide dielectric thin film by a simple and inexpensive wet coating method using a solution containing metal ions, and a capacitor and a semiconductor device using the same.

[0002]

2. Description of the Related Art Conventionally, methods such as sputtering, electron beam heating evaporation, resistance heating evaporation, and chemical vapor deposition have been used for forming a metal oxide thin film. It requires equipment and gas exhaust equipment, and it is difficult to form a large area thin film.
It was difficult to reduce manufacturing costs.

[0003] On the other hand, a wet coating method such as spin coating is an effective method for reducing the manufacturing cost because the apparatus is simple and the area can be easily increased. As a method for forming an oxide thin film or a metal thin film using a wet coating method, a method using a solution containing a peroxide is disclosed in JP-A-2-254172.

[0004]

In the above-mentioned conventional wet coating method, the heat treatment temperature after coating is 400 to 7%.
Since the temperature is as high as 00 ° C., it has been impossible to form a thin film on a substrate containing a material such as a resin having low heat resistance.

An object of the present invention is to provide a semiconductor device using an inexpensive oxide dielectric thin film, which solves the problem of the heat treatment temperature in the conventional coating method and has increased process flexibility. Further, the present invention provides a method for manufacturing such an oxide dielectric thin film and a capacitor using the same.

[0006]

In order to achieve the above object of the present invention, the type of metal salt contained in a coating solution for forming an oxide dielectric thin film and the atmosphere in a heat treatment process are examined. A method for lowering the heat treatment temperature required for converting an amorphous thin film into a crystalline oxide thin film was found.

In the method for producing an oxide thin film according to the present invention,
An aqueous solution containing a metal polyacid having a peroxide group is used as the coating solution. The solution can be prepared by allowing an aqueous solution of hydrogen peroxide to act on a metal, metal carbide, or organometallic complex. The polyacid-containing metal comprises at least one element selected from the group consisting of tungsten, molybdenum, tantalum, niobium, titanium, and zirconium. The composition formula of the polyacid is MOx.nH2O2.mH2O (where M is a metal, x is 1/2 of the valence of metal M, n is 0 or more and 1 or less, m
Takes a value of 0.1 or more and 4 or less). This is because, if it is not within this range, the solution may precipitate or the coating film is crystalline, resulting in poor flatness of the film. In addition to polyacids, if necessary, alkali metals (lithium, sodium, potassium), alkaline earth metals (magnesium, calcium, strontium, barium), rare earth metals (scandium, yttrium, lanthanum, lanthanoid series elements) , Lead, bismuth and at least one acid selected from the group consisting of nitric acid, hydrochloric acid, and organic acids (acetic acid, oxalic acid, benzoic acid, formic acid, etc.) or a mixture thereof. An aqueous solution of salt is added. The acid is not particularly limited as long as the acid component volatilizes or decomposes and is released into the gas phase when the coating film is heat-treated. When a solution contains a plurality of metal ions, the ratio of the metal ions is matched with the stoichiometric composition of the compound forming the target thin film. Also, if the concentration of the metal ions contained in the polyacid is too high, the gelation of the solution proceeds extremely rapidly or precipitates,
It can be a significant obstacle to application. Therefore, it is desirable that the concentration of metal ions be 5% or less by weight. However, if the concentration is too low, the film thickness obtained by one application becomes thin, so that the concentration is preferably 0.2% or more.

Depending on the type of the base, a nonionic surfactant such as ethyl cellosolve or polyoxyethylene ether may be added to the coating solution in a volume ratio of 5 to the aqueous solution of the metal salt in order to improve the wettability during spin coating. It is desirable to add about twice. The surfactant is not limited to the above-mentioned type as long as the addition of the surfactant does not cause precipitation or separation of the solution.

The coating film after spin coating is heated in an oxidizing atmosphere to form an oxide thin film. It is desirable to perform the heat treatment in an atmosphere to which an oxygen gas at a pressure of 1 Pa or more is added in order to promote the oxidation reaction. In consideration of the simplicity of the device, the oxygen partial pressure is desirably 1 atm or less. Furthermore, the effect that the oxidation reaction is remarkably accelerated when the atmosphere contains steam at a pressure of 1 Pa or more and a partial pressure of the saturated steam pressure or less at the heat treatment temperature, particularly when the heat treatment is performed at a low temperature of about 100 to 400 ° C. There is. Before heat treatment, the coating film contains moisture and peroxide groups, which evaporate at a relatively low temperature in the initial stage of heat treatment, resulting in non-uniform water and peroxide group contents inside the coating film. Conventionally, heat treatment at a temperature of 400 ° C. or less has been impossible because this hinders the oxidation reaction. When the heat treatment is performed in an atmosphere containing water vapor, the oxidation reaction proceeds rapidly even at a low temperature of 400 ° C. or less without such a problem, so that an oxide thin film can be formed at a low temperature. On the other hand, when a metal such as titanium or zirconium having high oxygen affinity is contained, a small amount of hydrogen gas having a partial pressure of about 1 to 10 kPa may have an effect of promoting decomposition instead. The lower limit of the temperature for the handling of the solution or the coating film and the oxidation reaction may be room temperature (20 ° C.) or higher in order to avoid solidification of the solution, but it is desirable to perform the oxidation reaction at 100 ° C. or higher from the viewpoint of efficiency.

A metal film such as platinum is formed on a silicon single crystal, an alumina sintered body, a metal such as an iron-nickel alloy or a copper alloy, a resin film such as a polyimide resin, an epoxy resin or a fluororesin, or a resin plate. By applying a solution to the upper portion and performing a heat treatment, a dielectric thin film can be formed.
Furthermore, a capacitor can be formed by forming a metal film such as platinum, chromium, nickel, or gold on the metal film and etching the metal film and the dielectric film. In addition, the metal film is etched using a mask during deposition or plating, and the dielectric film is subjected to an insolubilization treatment of the coating film by radiation irradiation before heat treatment after coating, and then an unnecessary portion is dissolved and removed, thereby etching the dielectric film. Can be omitted.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

(Embodiment 1) 1 g of titanium powder having a particle size of 10 μm or less is dissolved in 1 liter of 30% hydrogen peroxide solution, excess hydrogen peroxide is decomposed by a platinum catalyst, filtered, and filtered. Obtain a polyacid peroxide solution. For 1 volume of this solution,
Ethyl cellosolve (5 volumes) was added to prepare a coating solution, which was spin-coated at 3000 revolutions per minute on a silicon substrate on which a platinum thin film was deposited. After coating, the coating was heated to 50 ° C. and dried for 5 minutes, and then coating and drying were repeated three times. Then at 250 ° C 5
Heat treatment in an electric furnace with oxygen gas containing
It went for 0 minutes. The obtained thin film was titanium dioxide having a thickness of 200 nm. The dielectric constant of this titanium dioxide thin film was 70.
The dielectric constant of the thin film obtained by forming a coating film in the same manner and performing a heat treatment in dry oxygen was 30.

[0013] Tantalum, zirconium, niobium and tungsten were also prepared with a polymetallic solution having the same metal molarity, and thin films of tantalum oxide, zirconium oxide, niobium oxide and tungsten oxide were formed in the same manner. When the dielectric constants of these thin films were measured,
The dielectric constants of the samples subjected to the heat treatment in the water vapor-containing atmosphere were 27, 15, 10, 8 in the above order, and those of the heat treatment in the dry oxygen were 20, 13, 9, 7, respectively.

(Embodiment 2) A titanium peroxide polyacid similar to that of Embodiment 1 of the invention is prepared, a 5-fold amount of ethyl cellosolve is added, and a 1 N aqueous solution of bismuth chloride is added to bismuth. The mixture was dropped and mixed with stirring so that the molar ratio of titanium was 4: 3 to obtain a coating liquid. This was spin-coated at 3000 revolutions per minute on a silicon substrate on which a platinum thin film was deposited. After coating, the coating was heated to 50 ° C. and dried for 5 minutes, and then coating and drying were repeated three times. Next, heat treatment was performed for 30 minutes in a dry oxygen stream and an oxygen gas stream containing 5% water vapor at a temperature in the range of 200 to 500 ° C. while changing the temperature. The thickness of any thin film
It was around 230 nm. The crystal structure of these thin films was analyzed by the X-ray diffraction method. FIG. 1 shows the change in the crystal phase of the thin film with respect to each heat treatment temperature and atmosphere. As shown in the figure, the generation temperature of the crystal phase having a layered structure exhibiting ferroelectricity is lower when heat treatment is performed in an oxygen atmosphere containing water vapor.

(Third Embodiment of the Invention) A titanium peroxide polyacid similar to that of the first embodiment of the invention is prepared, and a 5-fold amount of ethyl cellosolve is added thereto. The strontium nitrate aqueous solution was dropped and mixed with stirring so that the molar ratio of barium, strontium and titanium was 1: 1: 2 to obtain a coating solution. This was spin-coated at 3000 revolutions per minute on a silicon substrate on which a platinum thin film was deposited. After coating, the coating was heated to 50 ° C. and dried for 5 minutes, and then coating and drying were repeated three times. Then 200-500 in dry oxygen stream and oxygen gas stream containing 5% water vapor
Heat treatment was performed for 30 minutes while changing the temperature in the range of ° C. Each thin film had a thickness of about 200 nm. About these thin films,
A sputtered platinum film was formed thereon, and a capacitor was formed between the sputtered platinum film and the underlying platinum thin film with the oxide thin film interposed therebetween. The dielectric constant was determined from the measured value of the capacitance. Also, 1MV /
The leakage current density under an applied electric field of cm was measured. These are shown in FIG. 2. As shown in FIG. 2, a thin film having a higher dielectric constant and less leakage can be formed at a lower temperature by heat treatment in the presence of water vapor.

Further, thin films were formed in the same manner for the substances shown in Table 1 below, and good characteristics were obtained.

[0017]

[Table 1]

The units in the table are as follows: temperature is ° C., there is no relative dielectric constant, leak current is A / cm ² , for example, 1e-8 is 1 × 10 ^-8
Is shown.

(Embodiment 4) A resin film 2 having a thickness of 100 μm is formed on a silicon substrate 1, a ground (copper) 3 having a thickness of 3 μm is formed on the resin film 2 by plating, and etching is performed by etching. A wiring pattern was formed. Further, a lower electrode layer (platinum / titanium two-layer film) 4 having a thickness of 0.2 μm is formed thereon by an electron beam evaporation method, and a dielectric thin film 5 having a thickness of 0.2 μm is formed thereon according to the third embodiment. It was formed in a similar manner. When the forming temperature was set to 220 ° C., no alteration or deformation was found in the underlying resin film 2.
Next, the lower electrode 4 and the dielectric thin film 5 are formed by ion milling.
Is formed thereon, and an interlayer insulating layer 6 made of a fluorine-based photosensitive resin having a thickness of 10 μm is formed thereon by a coating method. Through holes are formed in the resin layer 6 to form a lower electrode wiring 7 and an upper electrode wiring. 8 (all copper, thickness 3 microns) was formed by plating. The capacitance of a capacitor with an electrode area of 100 microns square is 70 pF, and the loss at 2 GHz is
It was 1.2%.

(Embodiment 5) A resin film 2 is formed on a substrate 9 on which a transistor chip and an integrated circuit chip 10 are mounted, and the surface is flattened. Next, wirings 3 were formed on the surface of the resin film 2 by plating, and connected to the respective chip components 10 by bumps or through holes 11. Further, a capacitor having a three-layer structure of the lower electrode 7, the dielectric thin film 5, and the upper electrode 8 was formed on the upper part by the same method as in the fourth embodiment of the invention. Further, an inductor 13 and a resistor 12 were formed thereon by plating, sputtering, and etching. Through the above steps, a high-frequency linear amplifier module was manufactured.

[0021]

As described above, the method for producing an oxide dielectric thin film according to the present invention is an inexpensive method and effective in lowering the temperature of the process. It can be applied to processes including low-resin resins, and can be used for integrated circuits and high-density mounting modules using the same, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in a crystal phase with respect to a heat treatment temperature of a bismuth titanate thin film in a dry oxygen atmosphere and a steam-containing oxygen atmosphere according to a second embodiment of the present invention.

FIG. 2 is a graph showing the influence of heat treatment temperature and atmosphere on the dielectric constant and leak current of a thin film of barium strontium titanate according to Embodiment 3 of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a capacitor according to a fourth embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional structure of a high-frequency linear amplifier module according to Embodiment 5 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Resin film, 3 ... Ground layer and wiring, 4 ... Platinum / titanium lower electrode layer,
5 ... dielectric thin film, 6 ... interlayer insulating resin layer, 7 ...
・ Lower electrode wiring and through hole, 8 ・ ・ ・ Upper electrode wiring and through hole, 9 ・ ・ ・ Metal substrate, 10 ・ ・ ・ Transistor and integrated circuit chip, 11 ・ ・ ・ Through hole and bump, 12 ・ ・ ・ Thin film Resistance, 13 ... Inductor.

Claims (9)

[Claims] 1. A semiconductor device having a dielectric thin film made of a heat-treated metal peroxide polyacid. 2. The semiconductor device according to claim 1, wherein said metal is at least one selected from tungsten, molybdenum, tantalum, niobium, titanium, and zirconium. 3. The method according to claim 1, wherein the dielectric thin film is formed by applying a solution containing a metal peroxide polyacid, forming an amorphous thin film, and then heating at a temperature of 400 ° C. or less. Semiconductor device. 4. The semiconductor device according to claim 3, further comprising at least one metal salt. 5. The metal salt according to claim 4, wherein at least one element selected from alkaline earth metals, rare earth metals, lead and bismuth and at least one element selected from nitric acid, hydrochloric acid and organic acids. A semiconductor device, which is a salt formed with an acid or a mixture thereof. 6. The semiconductor device according to claim 3, wherein the semiconductor device is heated in an atmosphere having an oxygen pressure of 1 Pa or more. 7. The semiconductor device according to claim 3, wherein the semiconductor device is heated in an atmosphere having an oxygen pressure of 1 Pa or more and a steam pressure of 1 Pa or more. 8. A semiconductor device according to claim 1, wherein a dielectric thin film is formed on a conductive material, and thereafter, a conductive material is formed on the oxide dielectric thin film, and a thin film capacitor comprising the same. A semiconductor device characterized by the above-mentioned. 9. The thin film capacitor according to claim 7, wherein the conductive substance as the base of the dielectric thin film is formed on the resin, and a semiconductor device having the same.