JPH09228049A - Raw compound for cvd of rare-earth element and film forming method using the compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deposit a material contg. a rare-earth element of specified composi tion by CVD and to secure a constant film forming rate for a long time by using a specified org. rare-earth element complex as the raw compd. for CVD. SOLUTION: An org. rare-earth element complex with 2,2,6,6-tetramethyl-3,5- octanedione as the ligand of the rare-earth element is used as the raw compd. for the CVD of a rare-earth element to deposit a rare-earth element or a rare- earth element-contg. material by CVD. The complex has a structure shown by the formula and has a low m.p. usable as the raw material for CVD, and the evaporating temp. is distinctly separated from the decomposing temp. Accordingly, the complex is heated above its m.p. and stably evaporated from the liq., and a film is efficiently formed by CVD.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material compound for CVD of a rare earth element or a rare earth element suitable for depositing a rare earth element or a substance containing the element by a chemical vapor deposition method (CVD method).

[0002]

2. Description of the Related Art As is well known, there are two methods of forming a single crystal thin film and a polycrystalline thin film, a dry process and a wet process. Generally, a thin film formed by a dry process is compared with a wet process. The dry process is often used because of the superior quality.

The dry process includes a physical film forming method such as a vacuum vapor deposition method, an ion plating method and a sputtering method, and a chemical film forming method such as a chemical vapor deposition method (CVD method). The latter CVD method, in particular, makes it easy to control the film formation rate and does not require film formation under high vacuum.
Moreover, it is widely used because it is suitable for mass production because it enables high-speed film formation.

In the CVD method, an organometallic complex is also used as a raw material compound, and when the vapor is decomposed to form a metal thin film, a thermal CVD method, a photo CVD method or a plasma CVD method is adopted. . As a raw material complex compound, generally, β whose organic part (ligand) is dipivaloylmethane, hexafluoroacetylacetone, etc.
-Diketone-based organometallic complexes have been used.

In recent years, rare earth elements (Y, Nd, etc.) or their oxides have been used as C as a thin film useful for superconductor materials and the like.
It has been proposed to form a film by the VD method. An organic rare earth element complex is advantageous as a raw material compound when depositing such a substance by the CVD method. Also in this case, it is possible to use an organometallic complex having a β-diketone such as dipivaloylmethane or hexafluoroacetylacetone as a ligand.

For example, JP-A-4-72066 and JP-A-4-74866 disclose carbon as an organic compound forming a complex with Group II metal, Group III metal, Group IVA metal and Group IB metal of the periodic table. 1,3-diketones having lower alkyl groups of the numbers 1 to 5 are described.

[0007]

SUMMARY OF THE INVENTION Since conventionally proposed organometallic complexes having a β-diketone-based organic compound as a ligand generally have a high melting point, when applied to a raw material compound of the CVD method, this is not less than the melting point. Since it cannot be heated to the temperature of 1, the raw material vapor must be generated by sublimation from the solid state.

Therefore, as the residual amount of the raw material in the raw material container decreases, the surface area of the raw material compound decreases and the vaporization rate slows down, and the amount of raw material vapor generated within a certain period of time decreases. However, there is a problem that a constant film forming speed cannot be secured for a long time. Further, when a compound thin film containing a metal of two or more elements is to be produced, it is difficult to control the composition for the same reason.

The organometallic complexes described in JP-A-4-72066 and JP-A-4-74866 are also characterized by high sublimation properties. As a raw material compound for CVD, vaporization from a solid state is required. Is intended, and therefore has the same problems as described above.

Further, an organometallic complex using a ligand containing fluorine in the molecule such as hexafluoroacetylacetone has a low melting point, but fluoride may be mixed as an impurity in the formed film, In this case, the properties of the film are significantly impaired.

Therefore, the present invention is intended to obtain an organometallic complex having a low melting point, particularly an organometallic complex of a rare earth element, which can solve the above problems.

[0012]

[Means for Solving the Problems] The inventors of the present invention have diligently studied in order to solve such problems, and found 2, 2, 6, 6
A complex of an organic rare earth element having a β-diketone of tetramethyl-3,5-octanedione as a ligand has a low melting point that can be used in a liquid state as a raw material compound for CVD, and has an evaporation temperature and a decomposition temperature. CVD that is clearly separated
It has been found that the method has extremely advantageous properties for the film formation by the method. Due to this characteristic, when this is used as a raw material compound for the CVD method, it is possible to evaporate from a liquid state, and to supply the raw material vapor of the rare earth element to the base material and analyze the content of the rare earth element on the base material. It was found that the problems described above can be solved because the output can be performed stably.

That is, according to the present invention, there is provided a raw material compound for CVD of a rare earth element used for precipitating a rare earth element or a substance containing the element by a CVD method,
A raw material compound for CVD of a rare earth element, which comprises an organic rare earth element complex using 2,2,6,6-tetramethyl-3,5-octanedione as a ligand of the rare earth element.

Further, according to the present invention, when a rare earth element or a substance containing the element is deposited on the substrate by the CVD method, 2,2,6,6-tetramethyl-3, An organic rare earth element complex having 5-octanedione as a ligand of the rare earth element is used, and the organic rare earth element complex is heated to a temperature equal to or higher than a melting point to evaporate the complex from a liquid phase of the complex. The present invention provides a method for forming a film of a rare earth element or a rare earth element-containing substance by the CVD method.

The organic rare earth element complex according to the present invention is represented by the general formula of Chemical formula 1 and is considered to be a novel compound. In the formula, REM represents a rare earth element. The rare earth element referred to in the present specification includes Y (yttrium). Therefore, Y is included in REM.

[0016]

[Chemical 1]

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A β-diketone-based organic rare earth element complex according to the present invention comprises a target rare earth element inorganic acid salt (chloride, nitrate, etc.) and 2,2,6,6-tetramethyl-3. , 5-octanedione was added dropwise to an aqueous alkaline solution (sodium hydroxide, ammonia, etc.) while stirring in a water-ethanol solution, and the resulting precipitate was collected by filtration and purified by recrystallization, distillation, etc. It can be obtained by the method of purification by.

Using the organic rare earth element complex thus obtained as a starting material compound for the CVD method and forming a film of the rare earth element or the rare earth element-containing substance by the CVD method,
For example, as shown in FIG. 1, a raw material container 2 containing the organic rare earth element complex 1 is placed in a thermostatic chamber 3 at a temperature higher than the melting point of the rare earth element (depending on the kind of the rare earth element, about 70 to 150 ° C.). And the inert carrier gas (for example, argon gas) 4 is introduced into the raw material container 2 while adjusting the flow rate by the flow meter 5 (for example, 5 to 500 ml / min), thereby accommodating the organic rare earth element complex. A generated gas stream is generated from the container 2.

The generated organic rare earth element complex vapor is introduced into the reaction tube 7 of the thermal decomposition furnace 6. Reaction tube (eg quartz tube)
7 is heated by a heater 8 and is a substrate 9 installed in the tube.
Is heated and maintained at a predetermined temperature (for example, 300 to 800 ° C.), the organic rare earth element complex is thermally decomposed and the rare earth element is deposited on the substrate 9 to form a film. The piping from the raw material container 2 to the pyrolysis furnace 6 is preferably kept warm at 80 to 160 ° C. by the heat retaining layer 10 or the heat retaining means in order to prevent condensation. Exhaust gas from the reaction tube 7 is discharged through a cooling trap 11. In the figure, 12 indicates a valve, and 13 indicates a rotary pump. Also,
When depositing an oxide of a rare earth element, the oxygen container 14
Then, an appropriate amount of gaseous oxygen is fed into the reaction atmosphere (for example, in the reaction tube 7) through the flow meter 15 and the valve 16. Further, in order to form a composite material with another element, although not shown, the raw material compounds of the other material are simultaneously introduced into the reaction tube 7.

[0020]

【Example】

[Example 1] Tris (2,2,6,6-tetramethyl-3,5- as shown in Chemical formula 2 was used as a raw material compound in a stainless steel raw material container 2 using the CVD equipment shown in FIG. Octanedionate) yttrium was added, and a magnesium oxide substrate was used as the substrate 9 to perform film formation thereon.

[0021]

Embedded image

The tris (2,2,6,6-tetramethyl-3,5-octanedionato) yttrium of Chemical formula 2 was prepared as follows.

12.5 g of yttrium nitrate hexahydrate was dissolved in 100 milliliters of water, and 2,2,6,6
-Tetramethyl-3,5-octanedione (17.5 g) and ethanol (100 milliliter) were added and stirred, and further aqueous ammonia was added dropwise to form a precipitate. Then, this was filtered, and the precipitate separated by filtration was dried under reduced pressure and then purified by distillation under reduced pressure to give 4.5 g of tris (2,2,6,6-
Tetramethyl-3,5-octandionato) yttrium was obtained. When the melting point of this compound was measured, it was 94-9.
6 ° C.

1 g of this compound was loaded into the container 2 and the thermostat 3 was kept at a constant temperature of 130.degree. While the magnesium oxide substrate 9 was heated and held at 700 ° C. by the heater 8, an argon gas as a carrier gas was passed through at 100 ml / min to introduce the compound into the quartz reaction tube 7. The piping from the container 2 to the pyrolysis furnace 6 was kept warm so as to be maintained at 140 ° C.

When a film forming operation was performed for 30 minutes under these conditions, a uniform yttrium thin film having a thickness of 2000 angstrom was obtained.

Tris (2, 2, 6, 6 loaded in container 2
The film forming operation was repeated under exactly the same conditions as described above, except that the amount of -tetramethyl-3,5-octanedionate) yttrium was changed to 2 g. Also in this case, the thickness is 2
A uniform yttrium thin film of 000 Å was obtained. That is, even if the amount of the raw material compound loaded in the container 2 was changed, a film having the same thickness could be formed. This indicates that the amount of evaporation from the raw material compound is constant during the processing time and the amount of decomposition is also constant.

Example 2 The same process as in Example 1 was repeated except that gaseous oxygen was added from the oxygen source 14 through the flow meter 15 and the valve 16 into the reaction tube 7 at a flow rate of 100 ml / min. I went for a minute. As a result, yttrium oxide thin films having the same thickness of 2900 angstroms were obtained for both raw material loadings of 1 g and 2 g.

Example 3 Using the tris (2,2,6,6-tetramethyl-3,5-octanedionate) neodymium shown in Chemical formula 3 as a raw material compound, a magnesium substrate was prepared in the same manner as in Example 1. The operation of forming a film on the above was performed.

[0029]

Embedded image

The tris (2,2,6,6-tetramethyl-3,5-octanedionato) neodymium of Chemical formula 3 was prepared as follows.

13.0 g of neodymium nitrate pentahydrate was added to 10 parts of water.
It is dissolved in 0 milimitle, and 2,2,6,6-tetramethyl-3,5-octanedione (17.5 g) and ethanol 100 milimitle are added and stirred, and ammonia water is added dropwise to form a precipitate. Then, this was filtered, and the precipitate separated by filtration was dried under reduced pressure, and then purified by distillation under reduced pressure to obtain 4.1 g of tris (2,2,6,6-tetramethyl-3,5-octanedionate) neodymium. Obtained. When the melting point of this compound was measured, it was 134 to 136.
° C.

1 g or 2 g of this compound was loaded into the container 2, and the thermostat 3 was kept at a constant temperature of 150 ° C.
3 to 3 under the same conditions as in Example 1 except that the pipes from the heat treatment furnace to the pyrolysis furnace 6 were kept warm so as to be maintained at 160 ° C.
A film forming operation for 0 minutes was performed. As a result, the raw material filling amount is 1
Both g and 2 g resulted in uniform neodymium thin films of the same thickness of 1800 Å. This indicates that the amount of evaporation from the raw material compound is constant during the processing time and the amount of decomposition is also constant.

Example 4 The same process as in Example 3 was repeated except that gaseous oxygen was added from the oxygen source 14 through the flow meter 15 and the valve 16 into the reaction tube 7 at a flow rate of 100 ml / min. I went for a minute. As a result, a neodymium oxide thin film having the same thickness was obtained, in which the raw material loadings were both 2500 g and 2500 g.

[Comparative Example 1] Yttrium tris (dipivaloylmethanato) having a melting point of 174 to 176 ° C in place of tris (2,2,6,6-tetramethyl-3,5-octanedionate) yttrium. Example 1 except that
The film was formed under the same conditions as described above. As a result, after 30 minutes, a thin film of yttrium having a material loading of 1 g and a thickness of 1900 angstroms and a material loading of 2 g having a thickness of 2400 angstroms was obtained. This means that
This indicates that the evaporation amount changed with time as the volume of the raw material in the container changed.

Comparative Example 2 The same procedure as in Comparative Example 1 was repeated except that gaseous oxygen was added from the oxygen source 14 through the flow meter 15 and the valve 16 into the reaction tube 7 at a flow rate of 100 ml / min. I went for a minute. As a result, the raw material filling amount 1
A thin film of yttrium oxide having a thickness of 2700 angstroms and a raw material filling amount of 2 g was 3200 angstroms.

Comparative Example 3 Tris (dipivaloylmethanato) neodymium having a melting point of 218 to 219 ° C. in place of tris (2,2,6,6-tetramethyl-3,5-octanedionate) neodymium. A film was formed under the same conditions as in Example 3 except that was used. As a result, the raw material filling amount 1 after 30 minutes
A thin film of neodymium having a thickness of 1600 angstroms was obtained for the sample of g, and a film thickness of 2100 angstroms for the sample having a raw material filling amount of 2 g. This indicates that the evaporation amount also changed with time as the volume of the raw material in the container changed.

Comparative Example 4 The same procedure as in Comparative Example 3 was repeated except that gaseous oxygen was added from the oxygen source 14 through the flow meter 15 and the valve 16 into the reaction tube 7 at a flow rate of 100 ml / min. I went for a minute. As a result, the raw material filling amount 1
A thin film of neodymium oxide having a thickness of 2000 angstroms and a raw material filling amount of 2 g was 2600 angstroms.

[0038]

As described above, the β-diketone-based organic rare earth element complex according to the present invention has a low melting point and high vaporization property,
And since the evaporation temperature and the decomposition temperature are different, CV
When used as a raw material compound for producing a thin film of a rare earth element or a rare earth element-containing substance by the D method,
It has an excellent advantage that it can be used in a liquid state, and because of this, the evaporation rate becomes constant, so that a stable film formation rate can be obtained, and further, high-speed and uniform film formation is possible.

Therefore, according to the present invention, it is possible to make a great contribution to the film forming technique of a rare earth element or a rare earth element-containing substance useful for a superconducting material or the like.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of equipment arrangement of equipment for carrying out a thermal CVD method.

[Explanation of symbols]

 1 Organometallic Complex 2 Raw Material Container 3 Constant Temperature Tank 4 Inert Carrier Gas 5 Flow Meter 6 Pyrolysis Furnace 7 Quartz Reaction Tube 8 Heater 9 Substrate 10 Heat Retaining Layer 11 Cooling Trap 12 Valve 13 Rotary Pump 14 Oxygen Source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C30B 25/02 C30B 25/02 Z 29/02 29/02 29/16 29/16

Claims (3)

[Claims] 1. A raw material compound for CVD of a rare earth element used for precipitating a rare earth element or a substance containing the element by a CVD method, comprising 2,2,6,6-tetramethyl-3,5- CVD of rare earth element consisting of organic rare earth complex with octanedione as ligand of rare earth element
Raw material compound. 2. The raw material compound for CVD according to claim 1, wherein the organic rare earth element complex is represented by Chemical formula 1. Embedded image 3. When depositing a rare earth element or a substance containing the element on a substrate by a CVD method, 2,2,6,6-tetramethyl-3,5-
CVD using an organic rare earth element complex with octanedione as a ligand of the rare earth element, heating the organic rare earth element complex to a temperature above the melting point, and evaporating the complex from the liquid phase of the complex Method of forming a rare earth element or a rare earth element-containing substance by the method.