JP3172665B2 - Dielectric thin film capacitor element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric thin film capacitor element used for electronic components such as an IC capacitor and a nonvolatile memory element, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, SiO ₂ (silicon oxide), SiN (silicon nitride), and the like have been used as dielectric thin films. However, in recent years, as electronic components have become smaller and more highly integrated due to advances in semiconductor technology, dielectric films have been made extremely thin and three-dimensionally structured in order to reduce the capacitor area. For this reason, the manufacturing process of the semiconductor element is becoming more and more complicated, and the fine processing technology is approaching its limit, causing problems in yield, reliability, and the like. Therefore, a dielectric thin film having a higher dielectric constant than that of the related art is required. At present, the development of a high dielectric thin film made of a perovskite oxide having a high dielectric constant has been actively pursued.

As a dielectric material of a perovskite oxide having such a high dielectric constant, PLT ((Pb, La) T
iO ₃ ) or PLZT ((Pb, La) (Zr, Ti)
Although there are Pb-based materials such as O ₃ ), there are other oxide high dielectric materials such as strontium titanate (SrTiO ₃ ) and barium strontium titanate ((Ba, Sr) TiO ₃ ). High dielectric thin films made of these dielectric materials are used for DRAM signal storage capacitors, MMI
C (Microwave Monolithic Integrated Cercuit) is used as a dielectric thin film capacitor element for an IC represented by a capacitor for a microwave element or the like.

[0004]

However, when a dielectric thin film capacitor element is manufactured using the above-mentioned conventional oxide high dielectric material, a leak current caused by oxygen deficiency in the crystal lattice of the dielectric thin film is large. However, there have been problems such as a failure to obtain good insulation properties and an increase in temperature dependence of leakage current. Therefore, when a conventional dielectric thin film capacitor element using an oxide high dielectric thin film is applied as a device, reliability has been a serious problem.

The following are conceivable causes of the above problem. In general, an oxide having a perovskite structure has oxygen lattice defects even in a single crystal. In an oxide thin film usually having a perovskite structure, oxygen lattice defects are generated during the growth of the thin film, so that a larger number of oxygen lattice defects are generated as compared with a bulk single crystal. Since electrons are generated as carriers due to the lattice defect of oxygen, a leak current is generated by voltage application. In addition, since the amount of generated carriers increases with an increase in temperature, it affects the temperature dependence of the leak current.

The present invention has been made to solve the above-mentioned problems, and has a sufficiently high dielectric constant.
It is an object of the present invention to provide a highly reliable dielectric thin film capacitor element having a small leak current and a small temperature dependency of the leak current, and a method of manufacturing the same.

[0007]

In order to solve the above-mentioned problems, the present invention provides a dielectric thin film capacitor element in which at least a lower electrode, a dielectric thin film and an upper electrode are laminated on a substrate, wherein the electrode is a metal electrode. The dielectric material
A thin film is laminated in contact with the metal electrode, and the thin film is
-Containing strontium titanate having a fluoride structure
Barium titanate strontium containing chromium or fluorine
Fluorine content which is composed of titanium and contained in the thin film
Is not less than 0.2 at% and not more than 0.5 at%.
And

According to the present invention, a thin film made of a fluorine-containing oxide having a perovskite structure is used as the dielectric thin film. Carrier generation due to oxygen vacancies in the generated crystal lattice can be suppressed, the leak current can be suppressed low, and the temperature dependence of the dielectric constant and the leak current can be reduced. Such an effect of the present invention occurs during the growth of a dielectric thin film because fluorine has a higher electron affinity than oxygen and thus easily bonds to metal atoms, and once fluorine and metal atoms bond, the bonding force is strong. It is considered that when the oxygen lattice defect enters the position, it becomes difficult to be desorbed.

[0009]

According to the present invention, since strontium titanate containing fluorine is used as the fluorine-containing oxide constituting the dielectric thin film, it has a sufficiently high dielectric constant, a small leakage current, and a small leakage current. A highly reliable dielectric thin film capacitor element having small temperature dependency can be realized.

[0011]

According to the present invention, since fluorine-containing barium strontium titanate is used as the fluorine-containing oxide constituting the dielectric thin film, it has a sufficiently high dielectric constant, a small leakage current, and a small leakage current. It is possible to realize a highly reliable dielectric thin film capacitor element having a small temperature dependency.

[0013]

According to the present invention, the content of fluorine contained in the fluorine-containing oxide constituting the dielectric thin film is optimized, so that the characteristics can be further improved.

[0015] In the present invention, the method for producing a dielectric thin film capacitor element and at least the lower electrode and the dielectric thin film and the upper electrode are sequentially laminated on a substrate, the lower electrode
After the metal electrode is formed as a perovskite-type acid
Or strontium titanate
Strontium fluoride in the strontium powder
Using a sputter target mixed and sintered
Forming the dielectric thin film by a sputtering method.
It is characterized by doing .

According to the present invention, since a sputtering method excellent in mass productivity is used, a sufficiently high dielectric constant is exhibited,
A highly reliable dielectric thin film capacitor element having a small leak current and a small temperature dependency of the leak current can be manufactured at low cost.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a cross-sectional structure of a dielectric thin film capacitor element manufactured according to an embodiment of the present invention. As shown in FIG. 1, this dielectric thin film capacitor element is provided on an n-type silicon substrate 1.
A silicon thermal oxide film 2, a Ti bonding layer 3, a Pt lower electrode layer 4, a dielectric thin film 5 made of a fluorine-containing oxide having a perovskite structure, and a Pt upper electrode layer 6 are sequentially formed.

Incidentally, the structure shown in FIG.
It is for evaluating the basic electrical characteristics of the dielectric thin film capacitor element according to the present embodiment described later, the structure of the dielectric thin film capacitor element according to the present invention is not limited to this, in fact, It can be used for various devices such as a memory device such as a DRAM and an MMIC with a free design as appropriate.

Next, the fabrication of the dielectric thin film capacitor element of the first embodiment will be described. First, a 200-nm-thick silicon thermal oxide film 2 was formed as an insulating layer on the surface of an n-type silicon substrate 1 by a thermal oxidation method. And
On this silicon thermal oxide film 2, a 30-nm-thick Ti adhesive layer 3 and a 200-nm-thick Pt lower electrode layer 4 were sequentially formed by DC sputtering.

Next, a fluorine-containing strontium titanate (SrTiO ₃ ) thin film (hereinafter referred to as a “srTiO _3” thin film) is formed on the Pt lower electrode layer 4 formed as described above as a dielectric thin film 5 made of a fluorine-containing oxide having a perovskite structure. ST
The formation of an OF thin film) was performed using an RF sputtering method (a high-frequency sputtering method). The sputter target used was obtained by sufficiently mixing strontium fluoride (SrF ₂ ) with strontium titanate (SrTiO ₃ ) powder, which is a perovskite oxide, and then sintering. Then, first, the surface of the sputter target is set to ST.
After pre-sputtering for 10 minutes under the same conditions as the OF thin film,
An OF thin film was formed. At this time, as shown in Table 1, the conditions of the preliminary sputtering and the film formation of the STOF thin film were as follows: the substrate temperature was 350 ° C., and the sputtering RF power was 4.25 W / c.
m ² , a sputtering pressure (gas pressure in a film forming chamber) of 2 Pa, and a sputtering gas of a mixed gas having a ratio of Ar: O ₂ = 1: 1. Under these conditions, a 200 nm-thick STOF thin film was formed. In this embodiment, the content of fluorine in the STOF thin film is set to 0.3 at%.

[0021]

[Table 1]

Thereafter, in order to evaluate the electrical characteristics of the dielectric thin film capacitor element according to the present embodiment, a Pt upper electrode layer 6 having a thickness of 100 nm
A circular thin film of 00 nm was formed by a vacuum deposition method, and the fabrication of the dielectric thin film capacitor element having the structure as shown in FIG. 1 was completed.

The present invention is not limited to the present embodiment with respect to the respective materials, thicknesses, forming methods, and the like of the substrate, the insulating layer, the adhesive layer, and the electrode layer.

For comparison, strontium fluoride (Sr) was used as a sputtering target when forming a dielectric thin film.
F ₂ ) free strontium titanate (SrTi
SrTi of the first comparative example in which a sintered product of O ₃ ) powder was used, and other manufacturing conditions were completely the same as those of the present embodiment.
A dielectric thin film capacitor element made of an O ₃ thin film (hereinafter, referred to as an STO thin film) was also manufactured.

Next, the evaluation of the electrical characteristics of the present embodiment and the first comparative example manufactured as described above will be described. As shown in FIG. 1, an electric field 7 was applied between the Pt upper electrode layer 6 and the Pt lower electrode layer 4, and the leak current and the dielectric constant were measured.

First, the measurement results of the dielectric constant, leak current, and increase rate of leak current (temperature dependence of leak current) of this embodiment (STOF thin film capacitor element) and the first comparative example (STO thin film capacitor element) Are shown in Table 2.

[0027]

[Table 2]

The measurement conditions at this time are as follows: the upper electrode layer-Pt
A voltage of 5 V and 10 Hz is applied between the lower electrode layers, and the dielectric constant and the leakage current I _l (A / cm ² ) are measured at room temperature (25
° C), and the increase rate of the leak current (temperature dependence of the leak current) is 1 when the leak current I _l (25 ° C.) at the measurement temperature of 25 ° C. is set to _1. (80 ° C.) (I _l (80 ° C.) /
I _l (25 ° C.). In Table 2, the STOF film indicates the measurement result of the STOF thin film capacitor element (this embodiment), and the STO film indicates the STOF film.
9 shows a measurement result of an O thin film capacitor element (first comparative example).

From Table 2, the dielectric constant of the present embodiment (STOF thin film capacitor element) is 150, which is the first comparative example (STOF thin film capacitor element).
It can be seen that the high dielectric constant is almost the same as the dielectric constant 152 of the O thin film capacitor element). The leakage current at room temperature (25 ° C.) of this embodiment is 4.9 × 10
^{-9, which} is a good value almost one digit smaller than the value of 3.8 × 10 ^-8 of the first comparative example. Further, the increase rate of the leak current (temperature dependence of the leak current) is 6.2 in the present embodiment, 11.6 in the first comparative example,
In the present embodiment, about one half of that of the first comparative example.
It can be seen that it has been successfully reduced.

Next, as a second embodiment, STOF
A plurality of STOF thin film capacitor elements in which the fluorine content of the thin film is changed are manufactured, and their dielectric constant, leak current,
A description will now be given of what evaluated the temperature dependence of the leak current.

In the first embodiment, the STOF thin film capacitor element manufactured with the STOF thin film having a fluorine content of 0.3 at% has been described. In the second embodiment, the STOF thin film having the STOF thin film having a varied fluorine content is used. A plurality of thin film capacitor elements were manufactured, and their characteristics were measured.

In the fabrication of the STOF thin film capacitor element according to the second embodiment, the fluorine content of the STOF thin film is changed by changing the mixing ratio of strontium fluoride (SrF ₂ ) of the sputter target when forming the dielectric thin film. Was changed to 0.2, 0.5, 0.6, 1.2 (at%), and otherwise the same as in the first embodiment.

The values of the dielectric constants of the device fabricated in the second embodiment, the first embodiment (fluorine content 0.3 at%) and the first comparative example (fluorine content 0 at%) FIG. 2 is a graph showing changes in the fluorine content (fluorine content). From FIG. 2, it can be seen that when the amount of fluorine in the STOF thin film is 0.5 or less, a sufficiently high and favorable value of about 150 is obtained. It is considered that when the amount of fluorine exceeds 0.5, crystallization hardly occurs in the STOF thin film, and the dielectric constant decreases.

The values of the leak currents of the device fabricated in the second embodiment, the first embodiment (fluorine content 0.3 at%) and the first comparative example (fluorine content 0 at%) are shown in FIG. FIG. 3 is a graph showing changes in the fluorine content (fluorine amount). From FIG. 3, if the amount of fluorine in the STOF thin film is 0.2 or more and 0.5 or less, 1 × 10 ^−8.
It can be seen that the following small good values are obtained.

The measurement temperature of 25 ° C. was obtained for each of the device manufactured in the second embodiment, the above-described first embodiment (fluorine content 0.3 at%) and the first comparative example (fluorine content 0 at%). Is the leak current I ₁ (25 ° C.) at 1, the rate of change (I ₁ (80 ° C.) / I ₁ (25 ° C.)) in the leak current I ₁ (80 ° C.) at the measurement temperature of 80 ° C., ie, the leak current FIG. 4 is a graph showing the temperature dependence of the temperature dependence of changes in the fluorine content (fluorine content). From FIG. 4, it can be seen that when the fluorine content of the STOF thin film is 0.2 or more and 0.5 or less, a small good value of 10 or less is obtained.

From the above evaluation of the characteristics of the first and second embodiments, it was found that the STOF thin film constituting the dielectric thin film capacitor element of the present invention had a fluorine content of 0.2 to 0.5. It can be seen that very favorable good characteristics can be obtained.

Next, a third embodiment will be described. In the third embodiment, instead of the STOF thin films of the first and second embodiments, as a dielectric thin film made of a fluorine-containing oxide having a perovskite structure, barium strontium titanate containing fluorine ((Ba _0.7 S
This is a dielectric thin film capacitor element using an r _0.3 ) TiO ₃ ) thin film.

In the fabrication of the dielectric thin film capacitor element according to the third embodiment, barium strontium titanate ((Ba _0.7 Sr _0.3 ) TiO), which is a perovskite oxide, is used as a sputter target when forming a dielectric thin film.
₃ ) Except that a powder obtained by sufficiently mixing strontium fluoride (SrF ₂ ) with the powder and sintering the powder was used, the procedure was exactly the same as in the first and second embodiments. In the third embodiment, the fluorine content was 0.10 at%.

Also, as in the first embodiment, the second
As a comparative example, a dielectric thin film capacitor element using a fluorine-free barium strontium titanate ((Ba _0.7 Sr _0.3 ) TiO ₃ ) thin film as a dielectric thin film constituting the dielectric thin film capacitor element was also manufactured. In addition,
In the preparation of the second comparative example, barium strontium titanate ((Ba _0.7 Sr _0.3 ) TiO ₃ ) powder containing no strontium fluoride (SrF ₂ ) was fired as a sputtering target when forming a dielectric thin film. The other conditions were the same as in the third embodiment.

The dielectric constant, leak current I _l (A / cm ² ), and leak current of the dielectric thin film capacitor elements of the third embodiment and the second comparative example are similar to those of the first embodiment. increase in the temperature dependence (measurement temperature 25 ° C. of the leakage current I _l (25 ° C.) 1 and leakage current I _l (80 ° C. of measurement temperature 80 ° C. when the the) of (I _l (80 ° C.) /
Table 3 shows the measurement results of each of I _l (25 ° C.))).

[0041]

[Table 3]

In Table 3, the addition of F (Ba _0.7 S
The (r _0.3 ) TiO ₃ film indicates the measurement result of the dielectric thin film capacitor element of the third embodiment, and is (Ba _0.7 Sr _0.3 ) T
The iO ₃ film shows the measurement result of the dielectric thin film capacitor element of the second comparative example.

From Table 3, the dielectric constant of the third embodiment is 1
It can be seen that the sample has a high dielectric constant almost equal to 30 and a dielectric constant 131 of the second comparative example. The leakage current at room temperature (25 ° C.) of the third embodiment is 8.9 × 1.
0 ^{-9, which} is a good value almost one digit smaller than the value of 7.5 × 10 ^-8 of the second comparative example, is obtained. Further, the increase rate of the leak current (temperature dependency of the leak current) is 8.6 in the third embodiment, and 13.6 in the second comparative example.
8 and that of the third embodiment are significantly reduced as compared with those of the second comparative example.

Fluorine-containing (Ba _0.7 Sr _0.3 ) Ti
As with the second embodiment, various characteristics of the dielectric thin film capacitor element composed of the O ₃ thin film were evaluated by changing the fluorine content. As a result, good results were obtained for those having a fluorine content other than 0.5 with respect to the dielectric constant, and the leak current and the temperature dependency of the leak current were good at 0.2 at% to 0.5 at%. The result was obtained.

That is, fluorine-containing (Ba _0.7 S
r _0.3 ) The dielectric thin film capacitor element composed of the TiO ₃ thin film has a fluorine content of 0.2 at% or more and 0.5 at% or less.
%, It was confirmed that a sufficiently high and good value of the dielectric constant could be obtained, and that there was an effect of reducing the leak current and the temperature dependence of the leak current.

[0046]

As described above, according to the dielectric thin film capacitor element and the method of manufacturing the dielectric thin film capacitor element of the present invention, a sufficiently high dielectric constant, a small leak current, and a temperature dependence of the leak current are obtained. And a highly reliable dielectric thin film capacitor element having a small size can be realized.

Therefore, according to the present invention, a DRAM capacitor having an IG level or higher and a low-cost high-performance MMI
When applied to an IC capacitor such as a C element, the reliability of the element can be greatly improved. In addition, the present invention
When applied to an insulating film for an L element, its high withstand voltage makes it possible to realize a highly reliable high-brightness EL element.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a dielectric thin film capacitor element according to the present invention.

FIG. 2 is a view showing a measurement result of a dielectric constant with respect to a change in the amount of fluorine of a STOF thin film in the STOF thin film capacitor elements of the first and second embodiments.

FIG. 3 is a diagram showing a measurement result of a leakage current with respect to a change in the amount of fluorine in a STOF thin film in the STOF thin film capacitor elements of the first and second embodiments.

FIG. 4 is a diagram showing a measurement result of a change ratio (temperature dependence of a leak current) of a STOF thin film in a STOF thin film capacitor element according to the first and second embodiments with respect to a change in a fluorine amount of the STOF thin film.

[Explanation of symbols]

 Reference Signs List 1 n-type silicon substrate 2 silicon thermal oxide film 3 Ti bonding layer 4 Pt lower electrode layer 5 dielectric thin film (STOF thin film) 6 Pt upper electrode layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoko Arai 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Noboru 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Masayoshi Kiba 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-63-291307 (JP, A) JP-A-7-38061 (JP, A) JP-A-61-242953 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/04 H01L 21/822 H01L 21/8242 H01L 27/108

Claims (2)

(57) [Claims] 1. A dielectric thin film capacitor element comprising at least a lower electrode, a dielectric thin film, and an upper electrode laminated on a substrate, wherein the electrode is a metal electrode, and the dielectric thin film is a metal electrode.
The thin film has a perovskite structure
Or strontium titanate containing fluorine
Of barium strontium titanate containing nitrogen
And the fluorine content in the thin film is 0.2 at
% To 0.5 at% or less . 2. A method according to claim 1 , wherein at least a lower electrode and a dielectric thin film
Dielectric thin film capacitor in which film and upper electrode are sequentially laminated
In the device manufacturing method, after a metal electrode as a lower electrode is formed,
Strontium titanate or titanite oxide
Barium strontium phosphate powder with strontium fluoride
Using a sputter target that is sufficiently mixed and sintered
Forming the dielectric thin film by a sputtering method
Dielectric thin film capacitor comprising a process
Device manufacturing method .