KR100592793B1 - Process for preparing hafnium oxide thin films by metal organic chemical vapor deposition - Google Patents

Abstract

In the present invention, tetrakis (3-methyl-3-pentoxy) hafnium (IV) [Tetrakis (3-methyl-3-pentoxy) hafnium (IV), Hf (mp) ₄ ] The present invention relates to a method for manufacturing a hafnium oxide thin film by metal organic chemical vapor deposition (MOCVD), the precursor of the present invention is a conventional Hf (O ^t Bu) ₄ (hafnium tetra- tert -butoxide It is suitable for MOCVD process because it has high vapor pressure when compared to), which is good for storage and use, and is useful for producing high quality hafnium oxide thin film by using it alone without supplying oxygen source.

Description

Method for producing hafnium oxide thin film by metal organic chemical vapor deposition method {PROCESS FOR PREPARING HAFNIUM OXIDE THIN FILMS BY METAL ORGANIC CHEMICAL VAPOR DEPOSITION}             

1 shows tetrakis (3-methyl-3-pentoxy) hafnium (IV), Hf compared to the existing precursor Hf (O ^t Bu) _4. (mp) ₄ ] thermogravimetric analysis (TGA) graph,

2 is a graph of vapor pressure according to the temperature of Hf (mp) ₄ compared to the existing precursor Hf (O ^t Bu) ₄ ,

3 is a graph showing the growth rate versus deposition temperature of the hafnium oxide thin film prepared according to the present invention,

4 is an X-ray photoelectron spectroscopic spectrum of a hafnium oxide thin film prepared according to the present invention,

5 is an X-ray diffraction pattern of a hafnium oxide thin film prepared according to the present invention.

The present invention relates to a method for manufacturing a hafnium oxide thin film, and more specifically, tetrakis (3-methyl-3-pentoxy) hafnium (IV) [Hf (mp) ₄ ] as a hafnium source without using an oxygen source. The present invention relates to a method for producing a high quality hafnium oxide thin film on a substrate by using metal organic chemical vapor deposition (MOCVD) as a single precursor.

Until now, SiO ₂ has been used as the gate dielectric material of silicon transistors, but as the design rules of semiconductor devices become smaller and smaller, tunneling current leakage and corresponding power dissipation at a thickness of less than 1.5 nm ) And the generation of heat have reached a serious problem. Therefore, there is a need to replace the SiO ₂ dielectric with another material having a high dielectric constant. Decades ago, many studies have been conducted to use Ta ₂ O ₅ instead of SiO ₂ , but ultimately due to various problems of Ta ₂ O ₅ , including small band offset values that affect leakage current The opinion that hafnium (HfO ₂ ) should be used is dominant.

Hafnium oxide thin film is a high- k material and is an important material to be used as a gate dielectric of next-generation semiconductor devices. Hafnium dioxide (HfO ₂ ) has a bulk dielectric constant of 40, which is quite high and does not react with silicon to form silicides (KJ Hubbard et al . , J. Mater. Res. , 1996, 11 , 2757) . The gap is 5.68 eV, which is effective for the suppression of tunneling phenomenon and thermal ion radiation and is very stable compound. Therefore, research on the production of hafnium oxide thin films has been actively conducted for many years, and the synthesis of raw material compounds of hafnium oxide and the manufacturing process of thin films are of great interest.

Initially used raw compounds were β-diketonates of hafnium such as Hf (tfac) ₄ and Hf (acac) ₄ (tfac = trifluoroacetylacetonate, acac = acetylacetonate; M. Balog et al., J. Electrochem.Soc., 1979, 126 , 1203; M. Balog et al . , J. Cryst.Growth , 1972, 17 , 298). Hafnium tetrachloride (HfCl ₄ ), hafnium t-butoxide [Hf (O ^t Bu) ₄ ; KS Mazdiyasni et al., USAF Technol. Doc. Rep. ASD-TDR-63-322 , 1963], and tetrakis (dimethylamido) hafnium (IV) [Hf (NMe ₂ ) ₄ , tetrakis (dimethylamido) hafnium, TDMAH], tetrakis (diethylamido) hafnium ( IV) Amido compounds of the form Hf (NR ¹ R ² ) ₄ , such as [Hf (NEt ₂ ) ₄ , TDEAH], tetrakis (ethylmethylamido) hafnium (IV) [TEMAH] (RG Gordon et al., S Suh, Chem. Mater. , 2001, 13, 2463; Y. Ohshita et al., J. Cryst. Growth , 2001, 233 , 292; DM Hausmann et al. , Chem. Mater. , 2002, 14 , 4350; A. Ogura et al. , Thin Solid Films , 2003, 441 , 161) are used as precursors for the MOCVD process and atomic layer deposition (ALD) process.

Of these, hafnium t-butoxide is used in MOCVD or plasma assisted MOCVD processes in the absence of oxygen supply, i.e. as a single precursor (S. Sayan et al . , J. Vac. Sci. Technol. A , 2002, 20 , 507; K.-J. Choi et al . , J. Electrochem.Soc. , 2002, 149 , F18; K.-J. Choi et al . , J. Mater.Res . , 2003, 18 , 60) .

Another unusual precursor is anhydrous Hf (NO ₃ ) ₄ (RC Smith et al . , Adv. Mater. Opt. Electron. , 2000, 10 , 105), but the compound is very reactive and solid at room temperature. There is a drawback of forming an oxide layer on the surface of a substrate such as silicon due to the great difficulty and strong oxidizing power.

In addition, hafnium tetrachloride is still used mainly in atomic layer deposition (ALD) processes, but it is inconvenient to handle due to its solid state at room temperature. Causes the same problem. Hafnium compounds of other halogen elements are also inconvenient to use and cause additional problems.

On the other hand, hafnium t-butoxide is highly reactive and difficult to handle in the thin film manufacturing process. Therefore, even if the compound is stored in a glove box, it is unstable to produce white decomposition products on the edge of the container. The use of this material in organic chemical vapor deposition (MOCVD) or atomic layer deposition (ALD) processes is a significant inconvenience. The most serious problem is clogging with hafnium t-butoxide, which breaks down the supply pipe of the precursor. In addition, hafnium t-butoxide has 30% residue in thermal weight analysis (see FIG. 1). Thus, when HfO ₂ thin film is prepared from this precursor, carbon contamination may occur, and catalytic hydrolysis may be performed even in trace amount of water. (catalytic hydrolytic decomposition) has a short shelf life due to reaction (PA Williams et al. , Chem. Vap. Deposition , 2002, 8 , 163). In the ALD process, which uses water as a source of oxygen to produce a hafnium oxide thin film, hafnium t-butoxide reacts with water remaining in the gas phase to prevent true atomic layer deposition and atomic layer chemical vapor deposition. , ALCVD).

To address the above disadvantages of hafnium t-butoxide, several compounds containing more complex alkoxides that coordinate more with the central metal, hafnium, have been proposed, which are tetrakis (1-methoxy-2-methyl-2 -Propoxy) hafnium (IV) [Hf (OCMe ₂ CH ₂ OMe) ₄ , Hf (mmp) ₄ ; PA Williams et al. , Chem. Vap. Deposition , 2002, 8 , 163], hafnium oxone neopentoxide [Hf ₃ (μ ₃ —O) (μ ₃ -ONep) (μ-ONep) ₃ (ONep) ₆ ; A. Abrutis et al., J. Cryst. Growth , 2004, 267 , 529], tetrakis (dimethylaminoethoxy) hafnium (IV) [Hf (OCH ₂ CH ₂ NMe ₂ ) ₄ , Hf (dmae) ₄ ; M.-K. Song, et al., Thin Solid Films , 2004, 450 , 272], which are difficult to handle due to their large ligands, which are directly liquid injection (DLI) MOCVD methods that are dissolved in solvent rather than directly used in simple MOCVD processes. To create a hafnium oxide thin film.

US Pat. No. 6,486,080 discloses a process for producing hafnium or zirconium oxide using alkoxide compounds of hafnium or zirconium as precursors. In this patent, hafnium alkoxide is represented by the general formula M (OR) ₄ (R is an alkyl or aryl group or a combination of alkyl or aryl), in which the precursor is reacted with an oxidant when used in chemical vapor deposition.

Therefore, the present invention adopts a MOCVD precursor material which does not cause the phenomenon of the precursor supply pipe clogging and the DLI-MOCVD method is not selected by selecting a ligand having a suitable size, and the surface is formed by the MOCVD method using this as a single precursor material. The present invention provides a method for producing a hafnium oxide thin film having a uniform, good coverage and good quality.

In order to achieve the above technical problem, the present invention provides a method for producing a hafnium oxide film using the hafnium compound represented by the formula (1) as a precursor of the MOCVD process.

<Formula 1>

Et = -CH ₂ CH ₃ , Me = -CH ₃

The present invention is explained in more detail below.

The method for preparing the hafnium oxide of the present invention is a precursor material of tetrakis (3-methyl-3-pentoxy) hafnium (IV) of Formula 1 [tetrakis (3-methyl-3-pentoxy) hafnium (IV), Hf (mp) ₄ ]. The Hf (mp) ₄ has an effect of reducing intermolecular interactions because the central hafnium atom is surrounded by a 3-methyl-3-pentoxy group larger than the t-butyl group of the conventional Hf (O ^t Bu) ₄ . Thus, Hf (mp) ₄ is much more stable than Hf (O ^t Bu) ₄ , but it is more responsive because the ligand is simpler than the ligands of the above compounds, which are more stable by filling the coordination sites of hafnium with complex ligands. There is this.

Prior art U.S. Patent No. 6.48608 million heading did not recognized at all for the invention As for Hf (mp) ₄ used in the merely be a formula only excellent point of ₄ Hf (mp) compared to ₄ (O ^t Bu) conventional Hf There is no mention that Hf (mp) ₄ can be used alone.

Due to the structural advantages described above, Hf (mp) ₄ used in the present invention has better physical properties when compared to Hf (O ^t Bu) _{4 in terms} of pyrolysis analysis and vapor pressure depending on temperature. It is possible to produce a high quality hafnium oxide thin film by using this precursor alone, without separately supplying it.

The precursor Hf (mp) ₄ according to the present invention reacts the amide complex of hafnium represented by the following formula (2) with the alcohol represented by the formula (3) as a starting material in a nonpolar solvent, or the hafnium chloride represented by the following formula (4) as the starting material It can manufacture by making the alkali metal salt of the alcohol shown by 5 react.

Hf (NR ' ₂ ) ₄

HOCMeEt ₂

HfCl ₄

M'OCMeEt ₂

Wherein R 'is methyl or ethyl and M' is Li, Na or K.

The synthesis is carried out in an inert argon or nitrogen atmosphere using a glove box or Schlenk line, and the structure and physical properties of the reaction product obtained in the synthesis are characterized by ¹ H nuclear magnetic resonance (NMR). Using carbon atom nuclear magnetic resonance ( ¹³ C NMR), elemental analysis (EA), mass spectroscopy, thermogravimetric / differential thermal analysis (TG / DTA) You can check it.

Process for manufacturing an oxide film is hafnium by using the precursors, Hf (mp) kept at a room temperature to 120 ℃ temperature of the vessel containing the _4, without using a carrier gas evacuating only Hf (mp) to the normal to the substrate ₄ Feeding to a chemical vapor deposition reactor (eg, a silicon substrate) and reacting at a substrate temperature in the range of 300 to 600 ° C.

In the present invention, in order to supply the precursor Hf (mp) ₄ in a sufficient amount to the reactor without using a carrier gas, it is important to maintain the temperature of the precursor container from 80 ° C to 120 ° C. This is because the vapor pressure of the precursor is low below 80 ° C. so that the precursor cannot be sufficiently supplied to the reactor, and above 120 ° C., the precursor itself pyrolyzes in the vessel. By using a carrier gas such as argon and using a bubbler, chemical vapor deposition can be performed even if the temperature of Hf (mp) ₄ is adjusted to room temperature.

In addition, it is preferable to maintain the temperature of the substrate at 300 ° C. or more in order to form a hafnium oxide thin film free of carbon contamination on the surface of the substrate by leaving all alkyl groups from the surface layer through the beta-hydrogen releasing reaction. This is because at lower temperatures it does not provide the energy needed to trigger the beta-hydrogen release of Hf (mp) ₄ . Therefore, according to the present invention, the hafnium oxide thin film having excellent properties can be made by maintaining the temperature of the substrate at 300 ° C. to 600 ° C., more preferably at 400 ° C. to 450 ° C.

According to the invention, Hf (mp) ₄ to the interface in the gas-phase decomposition of the clogging or the precursor of the precursor supply lines that the process conditions occur than in the method to write the old Hf (O ^t Bu) ₄ with a single precursor It is possible to produce a hafnium oxide thin film having no problem of forming an oxide film and having excellent characteristics.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the following examples are merely examples of the present invention, and the claims of the present invention are not limited thereto.

Tetrakis (3-methyl-3-pentoxy) hafnium (IV) [Hf (mp) ₄ Synthesis

<Example 1>

Tetrakisdiethylamidohafnium (IV) (5.00 g, 10.7 mmol) was dissolved in a flame dried 125 mL Schlenk flask containing hexane (50 mL). The solution was slowly added to hexane (30 mL) in which mpH (3-methyl-3-propanol, 3-methyl-3-propanol) (4.37 g, 47.1 mmol) was dissolved and stirred for 12 hours. The solvent was removed under reduced pressure and distillation under reduced pressure (130 ° C./10 ⁻² Torr) gave 6.13 g of the title compound as a yellow liquid (yield: 98.2%).

¹ H NMR (C ₆ D ₆ , 300.13 MHz): δ 1.03 (t, 24H, J = 7.5 Hz, CCH ₂ C H ₃ ), 1.22 (s, 12H, CC H ₃ ), 1.54 (q, 16H, J = 7.5 Hz, CC H ₂ CH ₃ ).

¹³ C { ¹ H} NMR (C ₆ D ₆ , 75.03 MHz): δ 79.9 (O C CH ₃ ), 35.6 (C ( C H ₂ CH ₃ ) ₂ ), 27.5 (C C H ₃ ), 8.80 (C (CH ₂ C H ₃ ) ₂ ).

Elemental Analysis C ₂₄ H ₅₂ O ₄ Hf {calculated (calculated)}: C, 49.43 (49.87); H, 8.99 (9.20).

<Test Example 1>

Thermogravimetric analysis (TGA) was performed to compare the thermal properties of Hf (mp) ₄ with Hf (O ^t Bu) ₄ .

Figure 1 is a two inde TGA graph of the precursor material, close to the 30% residue in the ₄ (O ^t Bu) Hf in the graph, but Hf (mp) Hf (mp) residues in less than 10% at ₄₄ The thermal properties of are much better than Hf (O ^t Bu) ₄ .

<Test Example 2>

Their vapor pressures were measured at several temperatures to compare the vapor pressures of Hf (mp) ₄ with Hf (O ^t Bu) ₄ .

2 is a graph showing the natural logarithm of the vapor pressure in mmHg for 1000 / T by measuring the vapor pressures of Hf (O ^t Bu) ₄ and Hf (mp) ₄ . From this graph, it can be seen that the vapor pressure of Hf (mp) ₄ is higher than that of Hf (O ^t Bu) ₄ in the entire temperature range of 25-60 ° C.

Chemical Vapor Deposition of Hafnium Oxide

<Example 2>

The silicon substrate to be deposited on the hafnium oxide thin film was treated with hydrofluoric acid and then mounted in the reactor, and the reactor was evacuated with an exhaust pump. The temperature of the vessel containing the Hf (mp) ₄ precursor synthesized according to Example 1 was raised to 120 ° C. and maintained at that temperature during the chemical vapor deposition reaction. No oxygen source was used separately.

The temperature of the silicon substrate mounted in the reactor was adjusted to 400 ° C., and a vapor of Hf (mp) ₄ precursor was introduced into the reactor for 30 minutes.

3 is an X-ray photoelectron spectroscopy spectrum of the thin film formed in Example 2, wherein the surface was cleaned by argon ion sputtering for 5 minutes to remove carbon contamination on the surface. Only the characteristic photoelectron peaks of hafnium and oxygen can be observed in this spectrum. In particular, near 284 eV, there are no C 1s peaks, indicating carbon contamination. From this, it can be seen that a hafnium oxide thin film having almost no carbon contamination was produced under the conditions of Example 2.

<Example 3>

Under the same conditions as in Example 2, the hafnium oxide thin film was manufactured while increasing the substrate temperature from 300 ° C. to 50 ° C. each.

4 is a graph showing a growth rate (μ / min) of 1000 / T of a hafnium oxide thin film grown at various temperatures (Arrhenius plot). The temperature of Hf (mp) ₄ was 120 ° C. The activation energy of the hafnium oxide thin film growth calculated from this data is 68.1 kJ / mol.

5 is an X-ray diffraction pattern of the hafnium oxide thin film prepared in Example 2. FIG. According to this, in the diffraction pattern of the hafnium oxide thin film prepared in the entire temperature range, only the peaks from the monoclinic hafnium dioxide can be examined.

The method for manufacturing a hafnium oxide thin film according to the present invention is characterized in that a hafnium oxide thin film is prepared using only Hf (mp) ₄ as a precursor material under conditions in which an oxygen source is not supplied separately, unlike a MOCVD process of hafnium oxide. In this way, a hafnium oxide thin film having excellent quality of almost no carbon contamination, little particles in the gas phase, and little silicon oxide film formed at the interface can be produced.

Claims (5)

A method for preparing a hafnium oxide film by a metal organic chemical vapor deposition (MOCVD) process using a hafnium compound Hf (mp) ₄ represented by Formula 1 below as a single precursor without a separate oxygen source: <Formula 1>

Wherein Et represents -CH ₂ CH ₃ and Me represents -CH ₃ . delete The method of claim 1, And maintaining the temperature of Hf (mp) _{4 in} the range from room temperature to 120 ° C. The method of claim 1, A method comprising using a silicon (Si) wafer, a germanium (Ge) wafer or a silicon carbide (SiC) wafer as a substrate. The method of claim 4, wherein Maintaining the temperature of the substrate in the range of 300 ° C to 600 ° C.

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