JPH09153598A - Dielectric thin film element and fabrication thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high reliability by forming a dielectric thin film using a perovskite-type sintered oxide as a target and a sputter gas containing neon thereby reducing the leak current. SOLUTION: A silicon thermal oxide film 2 is formed, as an insulating layer, on the surface of an n-type silicon substrate 1. A Ta adhesive layer 3 and a Pt lower electrode layer 4 are then formed sequentially by sputtering on the silicon thermal oxide film 2. Subsequently, a strontium titanate (SrTiO3 ) dielectric thin film is deposited, as a dielectric thin film 5 on the Pt lower electrode layer 4. More specifically, the SrTiO3 dielectric thin film is deposited by RF sputtering using a sintered oxide of SrTiO3 as a sputter target in an atmosphere of sputter gas ratio of Ne/O2 =5/5 in deposition chamber. After depositing the SrTiO3 dielectric thin film, an oxygen atmosphere is brought into the deposition chamber and cooled down to the room temperature. Finally, a Pt upper electrode layer 6 is formed on the dielectric thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI and a DRAM.
Memory cell, MMIC (Microwave MonolithicIntegr
TECHNICAL FIELD The present invention relates to a method of manufacturing a dielectric thin film element used for a capacitor for a gated circuit) and a dielectric thin film element.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, SiO ₂ (silicon oxide), SiN (silicon nitride), etc. have been used as a dielectric thin film. 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 conventional one is required, and at present, a high dielectric thin film made of a perovskite type oxide having a high dielectric constant is actively developed.

As a dielectric material of such a perovskite type oxide exhibiting a high dielectric constant, PLT ((Pb, La) T
iO ₃ ) and PLZT ((Pb, La) (Zr, Ti)
There are also Pb-based materials such as O ₃ ), but in addition to this, there is strontium titanate (SrTiO ₃ ). This SrT
iO ₃ is also useful as a capacitor for MMIC and DRAM, and many studies have been conducted on thinning it using a sol-gel method, a sputtering method, or the like.

As a material other than the above, there is titanium oxide (TiO ₂ ) which has a bulk dielectric constant of 180 and which has a high dielectric constant of about 50 when thinned. TiO ₂
Is not a multi-element system like PZT, PLZT and SrTiO ₃ , and the process is easy with only one element.
It is expected as a material for capacitors used in ICs and DRAMs.

On the other hand, as a method of manufacturing a dielectric thin film element, a sintered body of a raw material powder placed in a vacuum chamber is used as a target, and an inert gas such as Ar and a reactive gas such as oxygen is introduced into the vacuum chamber. A sputtering method in which plasma is generated to form a film is used as a useful means. In this sputtering method, a high-frequency electric field is applied to the target from outside to generate plasma of gas introduced into the vacuum chamber, and the target constituent elements in the form of atoms, ions, molecules, and clusters are made to face the target from the target surface. This is to deposit a thin film on a substrate that has been arranged. In addition, various studies have been made in view of the fact that a dielectric thin film can be formed at a low temperature as compared with other film forming methods and the mass productivity is excellent.

[0006]

However, in the above-mentioned conventional dielectric thin film element, the characteristics of the dielectric thin film itself constituting the element have not reached the practical level sufficiently.
For example, Pb-based dielectric thin films such as PLT and PLZT are
Pb or PbO easily evaporates and separates from the film, and it is difficult to control the composition. Therefore, sufficient reproducibility of electric characteristics is not obtained. Further, the conventional SrTiO ₃ dielectric thin film has a problem that when the dielectric thin film is sandwiched by electrodes, a large leak current is generated between the electrodes.

Further, even the conventional TiO ₂ dielectric thin film has a problem that when the dielectric thin film is sandwiched by electrodes, a large leak current is generated between both electrodes.

The present invention has been made in order to solve the above problems and shows a sufficiently high dielectric constant,
An object of the present invention is to provide a highly reliable dielectric thin film element manufacturing method with a small leak current and a dielectric thin film element.

[0009]

In order to solve the above problems, the present invention provides a method of manufacturing a dielectric thin film element comprising at least an electrode and a dielectric thin film, wherein a perovskite type oxide sintered body is used as a target and neon is used. A dielectric thin film is formed by a sputtering method using a sputtering gas containing

Further, in the present invention, in the above-mentioned method for manufacturing a dielectric thin film element, the sputtering gas containing neon is a mixed gas of neon and oxygen.

Further, in the present invention, in the above-mentioned method for manufacturing a dielectric thin film element, the target is made of strontium titanate.

Further, according to the present invention, in a method of manufacturing a dielectric thin film element comprising at least an electrode and a dielectric thin film,
A dielectric thin film is formed by a sputtering method using a target made of titanium or titanium oxide and a sputtering gas containing neon.

The operation of the method for manufacturing a dielectric thin film element of the present invention is as follows. In the sputtering method, when neon is mixed with oxygen as a sputtering gas, the amount of O ⁺ in plasma can be increased as compared with the case where argon is mixed. Since O ⁺ has a very strong oxidizing power, oxygen lattice defects in the crystal lattice of the dielectric thin film are efficiently compensated, and generation of carrier electrons due to oxygen deficiency is suppressed. Furthermore, neon has a larger peening effect and is more likely to enter the crystal lattice, as compared with argon, so that lattice distortion increases and the dielectric constant can be increased. It should be noted that this peening effect can be obtained by another dielectric thin film forming method, for example, a CVD method,
This is an effect unique to the sputtering method, which cannot be obtained by the sol-gel method or the reactive vapor deposition method.

By virtue of the above-described actions, according to the present invention, it is possible to realize a highly reliable dielectric thin film element having a sufficiently high dielectric constant, a small leak current.

Further, according to the present invention, in a dielectric thin film element comprising at least an electrode and a dielectric thin film, it is assumed that the dielectric thin film contains 0.1 to 1 at% of neon.

Further, in the present invention, in the above-mentioned dielectric thin film element, the dielectric thin film is made of strontium titanate.

Further, in the present invention, in the above-mentioned dielectric thin film element, the dielectric thin film is made of titanium oxide.

In the dielectric thin film element manufactured by the method for manufacturing a dielectric thin film of the present invention as described above, the dielectric thin film containing 0.1 to 1 at% of neon is contained in the film. The dielectric thin film element has a sufficiently high dielectric constant, a small leak current, and is highly reliable.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments 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 element manufactured according to the first embodiment of the present invention. As shown in FIG. 1, this dielectric thin film element comprises a silicon thermal oxide film 2, a Ta adhesive layer 3, a Pt lower electrode layer 4, a dielectric thin film 5, on an n-type silicon substrate 1.
The Pt upper electrode layers 6 are sequentially formed.

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

Next, the production of the dielectric thin film element of this 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. Then, a Ta adhesion layer 3 having a film thickness of 30 nm and a film thickness of 20 are formed on the silicon thermal oxide film 2.
The 0 nm Pt lower electrode layer 4 was sequentially formed by the DC sputtering method.

Next, the process of forming a strontium titanate (SrTiO ₃ ) dielectric thin film as the dielectric thin film 5 on the Pt lower electrode layer 4 thus formed will be described. In this embodiment, the sputtering target is Sr.
Using a TiO ₃ oxide sintered body, as a film forming condition, an atmosphere having a sputtering gas ratio Ne / O ₂ = 5/5 is set in the film forming chamber.
The pressure in the film formation chamber is kept at 2 Pa, the substrate temperature is 350 ° C., the sputtering power is 200 W, and the SrT film having a thickness of 240 nm is formed by the RF sputtering method (high-frequency sputtering method).
An iO ₃ dielectric thin film was formed.

Then, in this embodiment, after the SrTiO ₃ dielectric thin film was formed as described above, the film forming chamber was filled with an oxygen atmosphere and cooled to room temperature at a cooling rate of about 3 ° C./min.

Then, in order to evaluate the electrical characteristics of the SrTiO ₃ dielectric thin film according to the present embodiment, a Pt upper electrode layer 6 having a thickness of 100 nm was formed in a circular shape having a diameter of 500 nm on the dielectric thin film 5 made of SrTiO _3. It was formed by the vacuum evaporation method, and the fabrication of the dielectric thin film element having the structure shown in FIG. 1 was completed. The content of Ne in the SrTiO ₃ dielectric thin film of this embodiment was 0.5 at%.

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

For comparison, the sputtering gas ratio Ar / O was used as the sputtering gas when the SrTiO ₃ dielectric thin film was formed.
_{A second} comparative example was also prepared in which ₂ = 5/5 and other manufacturing conditions were exactly the same as those of the present embodiment.

Next, the evaluation of the electrical characteristics of this 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 to measure the leak current and the dielectric constant.

First, the results of measuring the dependence of the leakage current density on the applied voltage in the present embodiment and the comparative example are shown in FIGS. 2 and 3, respectively. 2 and 3, the horizontal axis represents the applied voltage (V) between the upper electrode and the lower electrode of the dielectric thin film element, and the vertical axis represents the leakage current density (A / c).
m ² ). According to FIG. 2 and FIG. 3, it is apparent that the present embodiment (when Ne is introduced) has a smaller leak current than the first comparative example (when Ar is introduced), and the leak current characteristic is significantly improved. You can see that For example, as shown in Table 1 below, the value of the leakage current density when the applied voltage is 5 V is 3.8 × 1 in the present embodiment (when Ne is introduced).
0 ^-10 , 3.5 × 10 ^-8 in the first comparative example (when Ar is introduced)
From this, it can be seen that the present embodiment has a smaller leakage current density value by two digits than the first comparative example and obtains good results.

For the measurement of the dielectric constant, 10 at room temperature.
As a result of performing at a modulation frequency of kHz, as shown in Table 1,
In this embodiment (when Ne is introduced), 125, the first comparative example (A
The value was 127 (at the time of introducing r), which was substantially equivalent to 127, but the values were sufficiently high, but no increase in the dielectric constant due to the above-mentioned peening effect was observed.

[0030]

[Table 1]

Next, S in this embodiment and the first comparative example
The results of observing the rTiO ₃ dielectric thin film will be described. First, FE-SEM (field emission scanning electron microscope)
As a result of observing the crystal grains of the SrTiO ₃ dielectric thin films of the present embodiment and the comparative example, the average grain size of the present embodiment is 100 nm, and the average grain size of the first comparative example is 100 nm. The size of the crystal grain of the present embodiment is about twice as large as 50 nm. From this, it is understood that in the present embodiment, since the crystal grains forming the SrTiO ₃ dielectric thin film grow large, the leak path at the grain boundary is reduced and the leak current can be reduced. Since this uses neon as the sputtering gas,
Compared to the case of using Ar, the incident energy of the emitted atoms from the target to the substrate is higher by Ne ⁺ than by Ar ⁺ ions, and the crystal grains forming the SrTiO ₃ dielectric thin film grow larger. It is believed that

In addition, XPS (X-ray Photo-erectron Spe
ctroscopy) of the present embodiment and the first comparative example.
As a result of measuring the rTiO ₃ dielectric thin film, the amount of oxygen vacancies in the film was about 10% smaller in the present embodiment than in the first comparative example. From this result, in the present embodiment, the oxygen deficiency amount is relatively small, and SrT
It is considered that generation of carrier electrons due to oxygen deficiency in the crystal lattice of the iO ₃ dielectric thin film is suppressed, which also contributes to the improvement of the leak current characteristic.

Next, in the formation of the SrTiO ₃ dielectric thin film, the content of neon was changed and the relationship between the content of Ne in the film and the leakage current characteristic was investigated. As a result, Ne
The effect of reducing the leak current was obtained when the content was in the range of 0.1 to 1 at%. When the Ne content in the SrTiO ₃ dielectric thin film is smaller or larger than this range,
The sufficient effect of reducing the leak current was not obtained.

Next, a second embodiment will be described in which a titanium oxide (TiO ₂ ) thin film is formed as a dielectric thin film. The structure of the dielectric thin film element manufactured in the second embodiment is different from that of the first embodiment shown in FIG. 1 in that the dielectric thin film 5 is the SrTiO ₃ dielectric in the first embodiment. Instead of using the thin film, only a TiO ₂ thin film is used, and the other structure is exactly the same as that of the first embodiment.

Also, the manufacturing of the dielectric thin film element of the second embodiment is different from that of the first embodiment only in the film forming process of the dielectric thin film 5, so only the process will be described. .

First, similar to the first embodiment,
After forming a silicon thermal oxide film 2 having a film thickness of 200 nm on the surface of the n-type silicon substrate 1, a T film having a film thickness of 30 nm is formed thereon.
a Adhesion layer 3 and Pt lower electrode layer 4 having a film thickness of 200 nm were sequentially formed. Then, titanium oxide (TiO 2) is formed as a dielectric thin film 5 on the Pt lower electrode layer 4 by a sputtering method.
₂ ) A thin film was formed. In the present embodiment, a Ti metal target is used as the sputtering target, and the film forming conditions are as follows: the film forming chamber has an atmosphere of sputtering gas ratio Ne / O ₂ = 5/5, and the pressure in the film forming chamber is 0.5 Pa. At a substrate temperature of 350 ° C. and a sputtering power of 300 W by an RF sputtering method (high frequency sputtering method).
A 0 nm Ne-containing TiO ₂ dielectric thin film was formed.
Then, after forming the TiO ₂ dielectric thin film as described above, the film formation chamber is made to have an oxygen atmosphere, and the cooling rate is about 3 ° C. /
Cooled to room temperature in minutes.

After that, as in the first embodiment, TiO 2
_{2 In} order to evaluate the electrical characteristics of the dielectric thin film, a Pt upper electrode layer 6 having a film thickness of 100 nm was formed in a circular shape with a diameter of 500 nm on the dielectric thin film 5 made of TiO ₂ by a vacuum deposition method to obtain a dielectric thin film. The fabrication of the device was completed. The content of Ne in the TiO ₂ dielectric thin film of the present embodiment is 0.
It was 5 at%.

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

For comparison, the sputtering gas ratio Ar / O ₂ = as the sputtering gas for forming the TiO ₂ dielectric thin film.
A second comparative example in which the manufacturing conditions were set to 5/5 and the other manufacturing conditions were exactly the same as in the present embodiment was also manufactured.

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

First, FIG. 4 shows the results of measuring the dependence of the leakage current density on the applied voltage in the second embodiment and the second comparative example.

In FIG. 4, the horizontal axis represents the voltage (V) applied between the upper electrode and the lower electrode of the dielectric thin film element,
The vertical axis represents the leakage current density (A / cm ² ). According to FIG. 4, it is apparent that the second embodiment (Ne + O ₂ gas) has a smaller leak current than the second comparative example (Ar + O ₂ gas), and the leak current characteristics are greatly improved. You can see that For example, as shown in Table 2 below,
The value of the leakage current density when the applied voltage is 5V, the second embodiment (Ne + O ₂ gas) at 9.1 × 10 ^-10, the second comparative example (Ar + O ₂ gas) at 8.5 × 10 ^{- 8} , it can be seen that the second embodiment has a smaller value of the leakage current density by two digits than the second comparative example, and a good result is obtained.

For the measurement of the dielectric constant, 10 at room temperature.
As a result of performing at a modulation frequency of kHz, as shown in Table 2,
The second embodiment (Ne + O ₂ gas) is 95, and the second comparative example (Ar + O ₂ gas) is 58, which shows that the second embodiment has a higher dielectric constant of 1.5 times or more, which is due to the peening effect. An increase in the dielectric constant appeared.

[0044]

[Table 2]

Next, the results of observing the TiO ₂ dielectric thin films of the second embodiment and the second comparative example will be described. First, FE-SEM (field emission scanning electron microscope)
As a result of observing the respective crystal grains of the TiO ₂ dielectric thin films of the second embodiment and the second comparative example, the average grain diameter of the second embodiment is 100 nm, and the average grain size of the second comparative example is 100 nm. The average grain size was 50 nm, and the grain size of the second embodiment was about twice as large.
From this, it is understood that in the second embodiment, since the crystal grains forming the TiO ₂ dielectric thin film grow large, the leak path at the grain boundary is reduced and the leak current can be reduced. This is neon (N
Since e) is used, the incident energy of the emitted atoms from the target to the substrate is A when compared with the case of using Ar.
It is considered that Ne ⁺ was higher than that of r ⁺ ions, and that the crystal grains forming the TiO ₂ dielectric thin film were grown large.

In addition, XPS (X-ray Photo-erectron Spe
As a result of the measurement of the TiO ₂ dielectric thin films of the second embodiment and the second comparative example, the amount of oxygen deficiency in the film is larger in the second embodiment than in the second comparative example. It was about 10% less than that of. From this result, the second embodiment has a relatively small amount of oxygen vacancies and suppresses the generation of carrier electrons due to oxygen vacancies in the crystal lattice of the TiO ₂ dielectric thin film, which also improves the leak current characteristic. It is thought that it contributes to.

Next, in the formation of the TiO ₂ dielectric thin film, the content of neon was changed and the relationship between the content of Ne in the film and the leakage current characteristic was investigated. As a result, the effect of reducing the leak current was obtained when the Ne content was in the range of 0.1 to 1 at%. And Ne in the film of the TiO ₂ dielectric thin film is
If the content is less or more than this range, the sufficient effect of reducing the leak current cannot be obtained.

In the second embodiment, TiO ₂
Although the Ti metal target was used as the sputtering target in the film forming process of the dielectric thin film by the sputtering method, a titanium oxide (TiO ₂ ) sintered body may be used instead.

[0049]

As described above, according to the method of manufacturing a dielectric thin film element and the dielectric thin film element of the present invention, a dielectric having a sufficiently high dielectric constant and a very small leak current and high reliability. It becomes possible to realize a thin film element.

Therefore, when the present invention is applied to capacitors such as MMIC and DRAM, it becomes possible to achieve excellent device characteristics and higher reliability.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing measurement results of applied voltage dependency of leakage current density according to the first embodiment.

FIG. 3 is a diagram showing measurement results of applied voltage dependency of leakage current density of the first comparative example.

FIG. 4 is a diagram showing measurement results of applied voltage dependency of leak current density in the second embodiment and the second comparative example.

[Explanation of Codes] 1 n-type silicon substrate 2 silicon thermal oxide film 3 Ta adhesive layer 4 Pt lower electrode layer 5 dielectric thin film 6 Pt upper electrode layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C30B 29/16 C30B 29/32 B 29/32 H01B 3/00 F H01B 3/00 H01L 21/203 S H01L 21/203 21/314 A 21/314 27/04 C 27/04 21/822 (72) Inventor Noboru Otani 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Mori Yano 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture (72) Inventor Naoko Arai 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Masayoshi Kiba Osaka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Japan

Claims (7)

[Claims] 1. A method of manufacturing a dielectric thin film element comprising at least an electrode and a dielectric thin film, wherein a dielectric thin film is formed by a sputtering method using a perovskite type oxide sintered body as a target and a sputtering gas containing neon. A method of manufacturing a dielectric thin film element, which comprises forming the same. 2. The method for manufacturing a dielectric thin film element according to claim 1, wherein the sputtering gas containing neon is a mixed gas of neon and oxygen. 3. The method for manufacturing a dielectric thin film element according to claim 1, wherein the target is made of strontium titanate. 4. A method of manufacturing a dielectric thin film element comprising at least an electrode and a dielectric thin film, wherein a dielectric thin film is formed by a sputtering method using a target made of titanium or titanium oxide and a sputtering gas containing neon. A method for manufacturing a dielectric thin film element, comprising: 5. A dielectric thin film element comprising at least an electrode and a dielectric thin film, wherein the dielectric thin film contains neon having a content of 0.1 to 1 at%. element. 6. The dielectric thin film element according to claim 5, wherein the dielectric thin film is made of strontium titanate. 7. The dielectric thin film element according to claim 5, wherein the dielectric thin film is made of titanium oxide.