JP2790581B2 - Production method of oxide-based dielectric thin film by CVD method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide-based dielectric thin film used for a dielectric memory or the like by a chemical vapor deposition (CVD) method.

[0002]

2. Description of the Related Art In recent years, integration of memory devices in semiconductors has been rapidly progressing. For example, the integration of dynamic random access memories (DRAMs) has progressed at a rapid rate of four times the number of bits in three years. This is for the purpose of speeding up the device, reducing power consumption, reducing cost, and the like. However, no matter how the degree of integration is improved, the capacitor that is a component of the DRAM must have a certain capacitance. For this reason, it is necessary to reduce the film thickness of the capacitor material, and there has been a limit to the thinning of the SiO ₂ used up to that time. Therefore, if the dielectric constant can be increased by changing the material, the capacity can be secured as in the case of thinning, so research using a high dielectric constant dielectric material for memory devices has recently attracted attention. .

As the performance required of such a capacitor material, it is most important that the thin film has a high dielectric constant and a small leak current as described above. That is, as long as a high dielectric constant material is used,
It is necessary to make the film as thin as possible and to minimize the leak current. The general development goals are generally SiO ₂
It is considered that the equivalent film thickness is desirably 1 nm or less and the leak current density when applying 1.65 V is desirably 10 ^-8 A / cm ² or less. In addition, in order to form a thin film on a capacitor electrode of a DRAM having a step, it is very advantageous from the viewpoint of processability that a film can be formed by a CVD method with good adherence to an object having a complicated shape. . From such a viewpoint, tantalum oxide, lead zirconate titanate (PZ)
T), lead lanthanum zirconate titanate (PLZT), strontium titanate, barium titanate, and other oxide-based dielectric thin films have been studied using various film forming methods. However, despite the fact that it is most advantageous to form a film by the CVD method, a major problem is that there is no compound having stable and good vaporization properties as a raw material compound for CVD (hereinafter referred to as a raw material) at present. I have. This is mainly because the β-diketone dipivaloylmethane (DPM) compound, which is frequently used as a raw material for CVD, does not have good vaporization characteristics due to heating. This point is suitable, for example, in the 52nd Annual Meeting of the Japan Society of Applied Physics, Proceedings No. 9a-P-11, and is considered to be a disadvantage due to the intrinsic instability of metal DPM compounds. Nevertheless, as described in, for example, the 52nd Annual Meeting of the Japan Society of Applied Physics, Proceedings No. 9a-P-6, the CVD method has been actively studied. In extreme cases, a situation has arisen in which raw materials must be disposable and a film must be formed. Therefore, due to the drawbacks caused by the above-mentioned raw materials, a technique for producing a dielectric thin film having good performance and good production reproducibility has not been established.

[0004]

As described above, in the production of an oxide-based dielectric thin film by the conventional CVD method,
Since the raw material for forming the oxide-based dielectric has poor vaporization and high-temperature stability, the raw material is heated at a low temperature to obtain a CV.
It is impossible to transport it stably to the D reaction section. Therefore, there is a major problem that it is difficult to control the composition and stable production of a dielectric thin film having good characteristics cannot be performed. On the other hand, if the raw material is heated at a high temperature in order to increase the vaporization efficiency, thermal decomposition or the like occurs during the transportation of the raw material, so that poor crystallinity of the film and deviation in composition are inevitable. In addition, there is a disadvantage that the raw materials must be disposable as described above. Also, if the reaction time is lengthened by suppressing the vaporization rate, the vaporized state of the raw material changes over time, so that the composition in the thickness direction of the formed film becomes inhomogeneous, and it is possible to avoid an increase in leak current. Absent. For this reason, there is a strong demand for the development of a raw material that can be vaporized stably and favorably at a low temperature, but no progress has been made in this regard.

[0005] The production method of the present invention is intended to solve the above-mentioned drawbacks in the conventional method of producing an oxide dielectric thin film by the CVD method. It is an object of the present invention to manufacture an oxide-based dielectric thin film for a capacitor having good performance while transporting the film to a part.

[0006]

Means for Solving the Problems The present inventors have proposed the aforementioned D
As a result of detailed studies on the vaporization properties of compounds in which a metal atom such as a PM compound is bonded to an organic group via an oxygen atom, among these compounds, alkaline earth metals such as Ba and Sr, and Pb and Ti It has been found that such compounds have poor vaporization and high temperature stability. Therefore, it has been found that when an oxide-based dielectric film containing these metal oxides as a main component is manufactured by the CVD method, it is inevitable that the controllability to the intended composition becomes difficult. Thus, the present inventors heated these compounds at a lower temperature than in the past and vaporized them stably without thermal decomposition, whereby the controllability of the composition was improved and the oxide-based dielectric thin film having the desired characteristics was obtained. Of the present invention with good reproducibility, and completed the present invention.

In the method for producing an oxide-based dielectric thin film by the CVD method according to the present invention, the raw material compound in which at least one of the vaporizing step and the transporting step of the raw material compound in which a metal atom is bonded to an organic group via an oxygen atom is used. With a vapor of an organic solvent having a boiling point of 100 ° C. or less.

In the method of the present invention, the metal atom of the starting compound in which the metal atom is bonded to the organic group via an oxygen atom is at least one selected from Pb, Ti, Zr, Ta and alkaline earth metals. Preferably it is.

Preferably, the metal atom of the starting compound used in the method of the present invention, in which the metal atom is bonded to an organic group via an oxygen atom, is Sr and / or Ba.

The compound used in the method of the present invention wherein a metal atom is bonded to an organic group via an oxygen atom is a metal acetylacetonate, dipivaloylmethanate, alkoxide, hexafluoroacetylacetonate, pentafluoropentane. It is preferably at least one selected from propanoyl pivaloyl methanates and their derivatives.

The compound used in the method of the present invention in which a metal atom is bonded to an organic group via an oxygen atom is Pb or an alkaline earth metal such as dipivaloyl methanate, hexafluoroacetylacetonate, or pentane. It is preferably at least one selected from fluoropropanoylpivaloylmethanate and alkoxides of Ti and Zr.

The compound used in the method of the present invention in which a metal atom is bonded to an organic group via an oxygen atom is Sr and / or
Alternatively, it is preferably Ba dipivaloyl methanate.

The organic solvent having a boiling point of 100 ° C. or lower used in the method of the present invention is a hydrocarbon, an alcohol, an ether,
It is preferably at least one selected from ketones and amines.

It is preferable that the organic solvent having a boiling point of 100 ° C. or lower used in the method of the present invention is at least one selected from diethyl ether, dimethyl ketone and tetrahydrofuran.

[0015]

In the present invention, the details of the action of the vapor of the organic solvent having a boiling point of 100 ° C. or less to be brought into contact with a compound in which a metal atom is bonded to an organic group via oxygen is unknown, but the vapor of the organic solvent is By acting on the compound to form a certain kind of low-boiling adduct, its vaporizability is improved even at low-temperature heating, and the stability of the vaporized substance is increased, and it is possible to feed the vaporized substance to the reaction section. It is considered to work.

[0016]

[Example 1] A strontium titanate-based oxide (SrT) prepared by a method of the present invention using a normal hot wall type CVD apparatus having a ternary raw material heating system.
An experiment was conducted to manufacture an iO ₃ ) dielectric thin film on a magnesium oxide substrate. As a raw material, an acetylacetonate derivative of Sr and Ti was used, and during heating, steam of dimethyl ketone (boiling point: 57 ° C.) as an organic solvent was flowed into and brought into contact with each other. As the reaction conditions, the heating temperature of the raw material was set at 185 ° C. for the Sr compound and 190 ° C. for the Ti compound, the carrier gas was argon, the reaction gas was oxygen, the pressure inside the reaction section (furnace) was 8 Torr, the substrate temperature was 700 ° C. The reaction time was 10 minutes. After the reaction, the resultant was naturally cooled to room temperature in an oxygen stream, and an oxide dielectric thin film having a thickness of about 60 nm was obtained. The crystallinity was examined by X-ray diffraction, and the dielectric constant and the leak current density when a DC voltage of 1.65 V was applied were measured. Table 1 shows the results.

[Comparative Example 1] A conventional CV using the same raw materials and reaction conditions as in Example 1 without mixing an organic solvent.
According to Method D, an oxide-based dielectric thin film was manufactured. T
For i, deposition on the substrate was observed, but for Sr, no deposition was observed, and it was found that heating at 185 ° C. caused almost no vaporization. Therefore, in Comparative Example 1, the reaction was carried out for 30 minutes at a heating temperature of the raw material of 230 ° C. for the Sr compound and 250 ° C. for the Ti compound, and the reaction was carried out to room temperature in an oxygen stream after the reaction as in the case of the method of the present invention. The film was naturally cooled to obtain a film having a thickness of 200 nm. The performance of this film was similarly examined. Table 1 shows the results.

[0018]

[Table 1] As is clear from Table 1, according to the method of the present invention, it is possible to obtain a dielectric thin film having good performance even when the heating temperature is lower than that of the conventional production method. In particular, as compared with the film formed by the conventional method, the film thickness is less than 1/3 and the leak current is reduced to 1/5.
It was able to be suppressed to 0 or less. In addition, when the repetition was examined by repeating the Examples and Comparative Examples 10 times under the same conditions as described above and the reproducibility was found, the thin film according to the method of the present invention showed a large variation in both the relative dielectric constant and the leak current density. It was found that the reproducibility was good.
On the other hand, the film obtained by the conventional method showed a large variation of ± 20% or more with respect to the values shown in Table 1 in both the relative dielectric constant and the leak current density.

Example 2 A lead zirconium titanate-based oxide dielectric thin film was manufactured using the same CVD apparatus as in Example 1 and using dipivaloylmethanate derivatives of Pb, Zr and Ti as raw materials. went. 20 raw materials each
While heating to 0 ° C., 190 ° C., and 180 ° C., a vapor of diethyl ether (boiling point: 35 ° C.) as an organic solvent was flowed into the container together with argon as a carrier gas, and brought into contact therewith. The substrate temperature was set to 630 ° C. using magnesium oxide as the substrate. Other conditions were the same as in Example 1 to produce a PZT-based oxide dielectric thin film. The thickness of the obtained film was 127 nm. The performance is shown in Table 2.

Comparative Example 2 In the same manner as in Example 2, except that no organic solvent was added, and for the same reason as in Comparative Example 1, the heating temperature of each raw material was as in Example 2. Higher, respectively, at 250 ° C, 220 ° C and 230 ° C. In this case, the film thickness was 381 nm. Table 2 shows the performance of the obtained thin films.

[0021]

[Table 2] As in the case of Example 1 from Table 2, according to the method of the present invention, even though the heating is performed at a lower temperature than that of the conventional production method, the relative dielectric constant,
It can be seen that an oxide-based dielectric thin film with much better leakage current density can be obtained. Further, as in Example 1, the same applies to Example 2 and Comparative Example 2 under the same conditions.
When the repetition was carried out 0 times and the reproducibility was examined, the film obtained by the method of the present invention did not show a large variation in both the relative dielectric constant and the leak current density. I found it.

Example 3 A barium strontium titanate-based oxide dielectric thin film was prepared using the same CVD apparatus as in Example 1 and using dipivaloylmethanate derivatives of Sr and Ba and Ti isopropoxide as raw materials. Was manufactured. At this time, while heating the Sr and Ba raw materials to 200 ° C. and 210 ° C., respectively, vapor of tetrahydrofuran (boiling point: 62 ° C.), which is an organic solvent, was flown into the gas together with argon as a carrier gas, and brought into contact therewith. Since Ti isopropoxide is a liquid, it was directly heated to 180 ° C. and vaporized. The substrate temperature was set to 635 ° C. using magnesium oxide as the substrate. Other conditions were the same as in Example 1, and 80 n
An oxide dielectric thin film having a thickness of m was manufactured. Table 3 shows the performance of the obtained oxide dielectric thin film.

Comparative Example 3 In the same manner as in Example 3, except that no organic solvent was added.
For the same reason as in Comparative Example 1, the heating temperature of the Sr and Ba raw materials was 240 ° C., which was higher than the respective cases.
It was kept at 60 ° C. In this case, the thickness of the thin film obtained is 1
It was 50 nm. Table 3 shows the performance of the obtained thin films.

[0024]

[Table 3] From Table 3, it can be seen that, as in the case of Examples 1 and 2, according to the method of the present invention, the relative dielectric constant of the thin film is smaller than that of the conventional method, although the heating is at a lower temperature than that of the conventional manufacturing method. It can be seen that an oxide-based dielectric thin film with much better leakage current density was obtained. Example 1
Similarly to Example 3 and Comparative Example 3, 10 repetitions were performed under the same conditions, and the reproducibility was examined. As a result, the film according to the method of the present invention showed a large variation in both the relative dielectric constant and the leak current density. No reproducibility was found, indicating that the reproducibility was better than that of the conventional film.

Example 4 A breakdown voltage was examined to verify application to a capacitor insulating film for a silicon integrated circuit.
A silicon oxide film having a thickness of 100 nm was formed on a Si substrate, and a platinum film having a thickness of 100 nm was further provided thereon as a lower electrode.
A barium strontium titanate-based oxide dielectric thin film having a film thickness of was manufactured. For comparison, the same method as in Comparative Example 3 was carried out in accordance with a conventional method without adding an organic solvent. At this time, in order to facilitate comparison, the film thickness was set to 80 nm, which is the same as that according to the method of the present invention. A platinum electrode having a diameter of 1.0 mm was formed on each of the obtained oxide-based dielectric thin films, and the breakdown voltage was measured.

FIG. 1A is a view showing the withstand voltage characteristics of a barium strontium titanate-based dielectric thin film obtained on a Si substrate by the method of the present invention in Example 4.
FIG. 1B is a diagram showing the breakdown voltage characteristics of a similar thin film similarly obtained by the conventional method.

As can be seen from FIGS. 1 (a) and 1 (b), the thin film obtained by the method of the present invention has less breakdown at a low voltage than the thin film obtained by the conventional method, and the breakdown voltage is lower. Improved.

In the first to third embodiments, in the step of vaporizing the raw material,
While heating the raw material, the vapor of the organic solvent having a boiling point of 100 ° C. or less was brought into contact with the raw material directly or together with the carry gas. After the raw material was heated and vaporized, the organic solvent was transferred to the reaction section when the vaporized substance was transported to the reaction section. It is also effective in a mode in which the vapor of the organic solvent is brought into contact only in the step of heating and vaporizing the raw material. In these cases, the vaporized material is sent to the reaction section in a stable state where changes such as decomposition do not easily occur even during transportation at a high temperature, and thus has the same excellent performance as obtained in Examples 1 to 3. An oxide-based dielectric thin film is obtained.

The oxide-based dielectric thin films obtained by the conventional method in Comparative Examples 1, 2, and 3 and Example 4 were excellent in spite of the fact that the crystals were oriented according to X-ray diffraction. Although it is not certain why it does not show properties, it is difficult to vaporize the raw material compound by heat, and in order to heat and transport the raw material compound to a high temperature, the raw material compound is decomposed while being vaporized or the vaporized substance is transported to the reaction section. It is presumed that various reactions take place, and this is probably due to the inhomogeneity of the composition in the thin film obtained on the substrate.

According to the method of the present invention, thin films of dielectric materials such as PLZT, barium titanate, tantalum oxide, and lead titanate were produced. As a result, in any case, a dielectric material having better performance than the conventional method was obtained. Thin films could be produced with good reproducibility.

Various kinds of organic solvents used in the method of the present invention were examined. For example, those having a boiling point of more than 100 ° C., such as n-butanol, cyclohexanone, dibutylamine and n-octane, were considered as starting compounds. Even when contact is made, the effect of improving the vaporization at low temperatures and stabilizing the vaporized raw material compounds at high temperatures as in the present invention does not appear, and the performance of the obtained thin film is obtained by the conventional method using no solvent at all. The performance was similar to that provided.

In the present invention, the organic solvent to be brought into contact with the starting compound is not particularly limited as long as it has a boiling point of 100 ° C. or lower, but preferred are alcohols such as methanol, ethanol and isopropanol, dimethyl ether, and the like. Chain and cyclic ethers such as diethyl ether, methyl ethyl ether, dioxane and tetrahydrofuran, dimethyl ketone, ketones such as methyl ethyl ketone, dimethylamine, amines such as diethylamine, n-hexane, dimethylbutane,
Aliphatic solvents such as hydrocarbons such as cyclohexane can be mentioned.

Further, as the raw material used in the present invention, if the compound is such that a metal atom is bonded to an organic group via an oxygen atom, the above-mentioned effect of the organic solvent is exhibited. Among them, Pb, Ti, Zr, Ta and alkaline earth metals are preferable as the metal, and acetylacetonate, dipivaloylmethanate, alkoxide, hexafluoroacetylacetonate, and pentafluoropropanoylpivalo of the above metals are preferable. Ilmethanate and derivatives thereof are preferably used.

[0034]

As described above, according to the method for producing an oxide-based dielectric thin film by the CVD method of the present invention, a raw material compound can be vaporized by heating at a low temperature and can be stably transported to a reaction section. This has the effect that the resulting oxide-based dielectric thin film has good performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing the withstand voltage characteristics of barium strontium titanate-based dielectric thin films obtained by the method of the present invention and the method of the prior art.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 27/108 (72) Inventor Toshihisa 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi 72) Inventor Takeharu Kuroiwa 8-1-1, Tsukaguchi-Honcho, Amagasaki-shi Mitsubishi Electric Corporation Co., Ltd. Materials and Devices Research Laboratory (72) Inventor Hisao Watai 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi Materials and Devices Research Mitsubishi Electric Corporation In-house (72) Inventor Takashi Higaki 4-1-1 Mizuhara, Itami-shi LSI Research Institute, Mitsubishi Electric Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/205 C23C 16/00 -16/56

Claims (8)

(57) [Claims] 1. When producing an oxide-based dielectric thin film by a CVD method using a raw material compound in which a metal atom is bonded to an organic group via an oxygen atom, at least one of a vaporizing step and a transporting step of the raw material compound In the step (a), a vapor of an organic solvent having a boiling point of 100 ° C. or less is brought into contact with the raw material compound, wherein the oxide-based dielectric thin film is produced by a CVD method. 2. The raw material compound in which a metal atom is bonded to an organic group via an oxygen atom is composed of Pb, Ti, Zr, T
2. The method for producing an oxide-based dielectric thin film according to claim 1, wherein the oxide-based dielectric thin film is at least one selected from a and an alkaline earth metal. 3. The method according to claim 1, wherein the metal atom of the starting compound in which the metal atom is bonded to the organic group via an oxygen atom is Sr and / or B
3. The method for producing an oxide-based dielectric thin film according to claim 1, wherein 4. A raw material compound in which a metal atom is bonded to an organic group via an oxygen atom is a metal acetylacetonate, dipivaloylmethanate, alkoxide, hexafluoroacetylacetonate, pentafluoropropanoylpivaloyl. 4. The method for producing an oxide-based dielectric thin film according to claim 1, which is at least one selected from methanates and derivatives thereof. 5. A raw material compound in which a metal atom is bonded to an organic group via an oxygen atom is Pb or an alkaline earth metal such as dipivaloylmethanate, hexafluoroacetylacetonate, or pentafluoropropanoylpivalo. Claim 1 characterized in that it is at least one selected from ilmethanates and alkoxides of Ti and Zr.
5. The method for producing an oxide-based dielectric thin film according to 2, 3, or 4. 6. The raw material compound in which a metal atom is bonded to an organic group via an oxygen atom is dipivaloyl methanate of Sr and / or Ba.
6. The method for producing an oxide-based dielectric thin film according to 2, 3, 4, or 5. 7. The oxide-based dielectric according to claim 1, wherein the organic solvent having a boiling point of 100 ° C. or lower is at least one selected from hydrocarbons, alcohols, ethers, ketones and amines. Manufacturing method of body thin film. 8. The method for producing an oxide dielectric thin film according to claim 1, wherein the organic solvent having a boiling point of 100 ° C. or lower is at least one selected from diethyl ether, dimethyl ketone, and tetrahydrofuran.