JP2005166965A - Method for manufacturing thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin film having high electric characteristics at a low temperature by a CVD method. <P>SOLUTION: After manufacturing a thin film by the thin film manufacturing method based on the CVD method for forming a film on a substrate heated to the decomposition temperature or more of raw material gas by using film formation gas consisting of the raw material gas and reaction gas, crystallization annealing processing is performed at a temperature lower than the film formation temperature of the thin film. As a thin film before the annealing processing, film formation gas in which the quantity of raw material gas having the highest decomposition temperature out of the raw material gas components is set to the same quantity or more of a succeeding process is introduced to form an initial layer, and then film formation gas in which the quantity of raw material gas having the highest decomposition temperature is set to the same quantity or less as that of the initial layer is introduced to form a 2nd layer and after. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film manufacturing method, and more particularly to a method of manufacturing an oxide thin film by a CVD method such as MOCVD.

  In recent years, high integration and high performance of semiconductor elements are required in the semiconductor field. As means for solving these demands, film formation by CVD (chemical vapor deposition) method, which is expected to be a dense film having excellent step coverage and few defects, has attracted attention.

  In order to meet these requirements, the introduction of new materials has also been proposed. In order to solve the problems at the time of introducing this new material and to solve problems such as element diffusion, it is required to further lower the film forming process temperature.

Also, high dielectric constant dielectric oxides such as Ta ₂ O ₅ , (Ba, Sr) TiO ₃ , SrTiO ₃ , Pb (Zr, Ti) O ₃ , SrBi ₂ Ta ₂ O ₉ , Bi ₄ Ti ₃ O _12, etc. ferroelectric _{oxide, IrO 2, RuO 2, SrRuO} 3, electrically conductive oxides such as _{LaNiO 3, (La, Sr)} MnO 3, a thin film made of a ferromagnetic oxide such as (Pr, Ca) MnO ₃ of Has attracted attention from applications such as highly integrated devices, low power consumption devices, nonvolatile memories, and capacitor electrode materials. However, when these films are formed at a low temperature, the films do not crystallize and do not function as various applications, the film composition near the interface with the base is different, and a large leakage current is generated. Various problems occur. For example, when oxygen in the film is deficient and good epitaxial growth is prevented, the insulating properties of the paraelectric oxide film and the ferroelectric oxide film are lowered, and the electrically conductive oxide film and the strong oxide film are strong. The magnetic oxide film has a problem that electric conductivity is lowered.

The problem of the present invention is to solve the above-mentioned problems of the prior art, by correcting a film composition deviation at the initial stage of film formation and controlling the composition in the film thickness direction when manufacturing a thin film by a CVD method at a low temperature, Provided is a method for producing a thin film having excellent electrical characteristics, in particular, a leakage current density of 1.0E-3 A / cm ² or less when 2 V is applied and a polarization reversal charge density of 25 μC / cm ² or more when 2 V is applied. There is.

  According to the first aspect of the present invention, the thin film manufacturing method of the present invention includes a raw material gas obtained by vaporizing a liquid obtained by dissolving a solid raw material or a liquid raw material in a solvent using a vaporization system, or sublimation from a solid raw material or evaporation from a liquid raw material. In a thin film manufacturing method by a CVD method in which a film forming gas containing a generated raw material gas and a reactive gas is introduced into a reaction chamber through a gas introducing means, and a film is formed on a substrate heated above the decomposition temperature of the raw material gas. When manufacturing a thin film composed of two or more layers, a deposition gas containing the source gas having the highest decomposition temperature among the source gases in an amount equal to or greater than that in the next deposition process is introduced into the reaction chamber. Form an initial layer, and then introduce a deposition gas containing the source gas having the highest decomposition temperature equal to or less than that in the initial layer film formation process to form the second and subsequent layers. It is characterized by.

By manufacturing a thin film composed of a plurality of layers using a film forming gas having a blending ratio as described above, crystallization is promoted and a thin film having excellent electrical characteristics, for example, a low leakage current density, It is possible to obtain a thin film having a high polarization inversion charge density and a good rise of the charge density at a low voltage. For example, 1.0E-3A / cm ² or less at 2V applied, preferably 1.0E-4 / cm ² or less of the leakage current density also,, 25μC / cm ² or more at 2V applied, preferably 30 .mu.C / cm ² or more A thin film having a polarization reversal charge density can be obtained.

According to claim 2, in the thin film manufacturing method, the temperature of the path from this system to the gas introduction means in the upper part of the reaction chamber, including the vaporization system, is precipitated or decomposed before the source gas reaches the substrate. It is characterized in that the film is formed at a temperature at which it does not occur.
By appropriately setting the temperature of the path or the like according to the raw material gas composition, generation of particles can be prevented and a thin film having desired electrical characteristics can be manufactured.

  According to claim 3, the thin film manufacturing method of the present invention also includes a raw material gas obtained by vaporizing a liquid obtained by dissolving a solid raw material or a liquid raw material in a solvent using a vaporization system, or sublimation from a solid raw material or evaporation from a liquid raw material. In accordance with a thin film manufacturing method by CVD, a film forming gas containing a source gas and a reaction gas generated by the above is introduced into a reaction chamber through a gas introduction means, and a film is formed on a substrate heated above the decomposition temperature of the source gas. After the thin film is manufactured, a crystallization annealing treatment is further performed at a temperature lower than the film forming temperature of the thin film.

  By performing the crystallization annealing treatment in the above-mentioned temperature range, it is possible to obtain a thin film with accelerated crystallization and excellent electrical characteristics, for example, a thin film having a low leakage current density and a high polarization inversion charge density. it can.

  According to claim 4, when the thin film before the crystallization annealing treatment uses a plurality of source gases as the source gas, the thin film before the crystallization annealing treatment follows the source gas having the highest decomposition temperature among the source gases. A film-forming gas containing the same amount or more as in the case of the film-forming process is introduced into the reaction chamber to form an initial layer, and then the source gas having the highest decomposition temperature is the same as in the case of the initial-layer film-forming process. A thin film in which a second and subsequent layers are formed by introducing a deposition gas containing an amount less than or equal to the amount is characterized.

  According to claim 5, (1) the upper electrode is formed after the crystallization annealing treatment, and then the recovery annealing treatment is performed under the same conditions as the crystallization annealing treatment, or (2) before the crystallization annealing treatment. An upper electrode is formed, and then an annealing process that serves as both a crystallization annealing process and a recovery annealing process is performed. By this recovery annealing treatment, damage to the base film during upper electrode film formation is recovered.

  According to a sixth aspect of the present invention, the annealing treatment is performed in an air atmosphere or an atmosphere having a higher oxygen concentration than the air atmosphere.

  According to a seventh aspect of the present invention, the annealing treatment is performed after the object to be annealed is previously charged in a furnace set at a predetermined temperature and a predetermined atmosphere and held for 30 minutes to 2 hours. The temperature and atmosphere of this pretreatment may be, for example, an oxygen atmosphere at 500 ° C. for 1 hour.

  According to the eighth aspect of the present invention, at least one gas selected from oxygen, ozone, dinitrogen monoxide, and mononitrogen dioxide is used in order to make the oxygen concentration higher than that in the air atmosphere.

According to a ninth aspect of the present invention, the upper electrode is formed by sputtering.
According to a tenth aspect of the present invention, the upper electrode is made of a noble metal-based material selected from Pt, Ir, and IrOx.

According to claim 11, the raw material is selected from Pb, Zr, Ti, Ba, Sr, Ta, Bi, La, Ru, Ir, Ni, Mn, Pr, Si, Al, Hf, Mg, Ca. It contains at least one element.
According to claim 12, the raw material is an organometallic compound as a raw material for MOCVD.

According to claim 13, the organometallic compound is Pb (thd) ₂ ((bis (2,2,6,6) tetramethyl (3,5) heptanedionate) lead), Zr (thd) ₄ (( Tetrakis (2,2,6,6) tetramethyl (3,5) heptanedionate) zirconium), Zr (dmhd) ₄ ((tetrakis (2,6) dimethyl (3,5) heptanedionate) zirconium), Ti (i-PrO) ₂ (thd) ₂ ((bisisopropoxide) (bis (2,2,6,6) tetramethyl (3,5) heptanedionate) titanium), Zr (MMP) ₄ (( Tetrakis (1) methoxy (2) methyl (2) propoxy) zirconium) and Ti (MMP) ₄ ((tetrakis (1) methoxy (2) methyl (2) propoxy) titanium) Features.

  According to the fourteenth aspect, when a film forming gas containing a Pb-containing source gas is used as the source gas, a film forming gas containing the same amount or more of the Pb-containing source gas as in the next film forming process is introduced into the reaction chamber. Then, the initial layer is formed, and then the second and subsequent layers are formed by introducing a film forming gas containing the Pb-containing source gas in an amount equal to or less than that in the initial layer forming process. Features. Thereby, a thin film with improved electrical characteristics such as leakage current density can be obtained.

According to claim 15, the gas comprising Pb (thd) ₂ , Zr (dmhd) ₄ or Zr (MMP) ₄ , and Ti (i-PrO) ₂ (thd) ₂ or Ti (MMP) _{4 as the} source gas. When a Pb (Zr, Ti) O ₃ thin film is manufactured using a film-forming gas containing, when the film forming gas composed of these raw materials is introduced into the reaction chamber to manufacture the thin film, this Pb-containing material gas is used. A film-forming gas containing the same amount or more as in the case of the next film-forming process is introduced into the reaction chamber to form an initial layer, and then this Pb-containing source gas is equal to or less than the amount in the case of the initial-layer film-forming process. The second and subsequent layers are formed by introducing a film forming gas containing the above-mentioned amount.

According to a sixteenth aspect of the present invention, the initial layer is formed so as to be thinner than the second layer. Thereby, a thin film having excellent electrical characteristics can be obtained.
According to a seventeenth aspect of the present invention, the thickness of the initial layer is set to 1/20 or less of the thickness of the second layer.
According to claim 18, the thickness of the initial layer is set to 20 nm or less.
By setting the thickness of the initial layer as described above, a thin film having a low leakage current density and a high polarization inversion charge density can be manufactured.

  According to the nineteenth aspect, at least one solvent selected from tetrahydrofuran, cyclohexane, ethylcyclohexane, and methylcyclohexane is used as a solvent for dissolving the raw material.

According to claim 20, the substrate used in the thin film manufacturing method has a plane orientation selected from Pt, Ir, Rh, Ru, MgO, SrTiO ₃ , IrO ₂ , RuO ₂ , SrRuO ₃ , and LaNiO _3. A substrate made of an oriented material is used.

According to Claim 21, the substrate is selected from Ir / SiO ₂ / Si, Ir / Ti / SiO ₂ / Si, Pt / Ti / SiO ₂ / Si, and SrRuO ₃ / Pt / Ti / SiO ₂ / Si. It is characterized by using the above.

According to claim 22, the thin film produced according to the present invention comprises a paraelectric dielectric oxide selected from (Ba, Sr) TiO ₂ and SrTiO ₃ , Pb (Zr, Ti) O ₃ , SrBi ₂ Ta ₂ O. ₉ , and a ferroelectric oxide selected from Bi ₄ Ti ₃ O _12, an electrically conductive oxide selected from SrRuO ₃ and LaNiO _3, from (La, Sr) MnO ₃ and (Pr, Ca) MnO ₃ It is a thin film of a selected ferromagnetic oxide.

According to a twenty- _{third aspect} , the Pb (Zr, Ti) O ₃ further contains at least one selected from Nb, La, Ca, and Sr.

According to claim 24, the thin film produced according to the present invention is a paraelectric dielectric oxide selected from SiO ₂ , TiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , MgO, ZrO ₂ , and HfO ₂ , It is a thin film of an electrically conductive oxide selected from IrO ₂ and RuO ₂ .

  According to the present invention, by using a film-forming gas having a raw material gas with a predetermined blending ratio, correcting a composition shift at the initial stage of film formation and controlling the composition in the film thickness direction, and after film formation, A thin film whose crystallization is promoted by annealing treatment under conditions, and has excellent electrical characteristics, for example, a low leakage current density, a high polarization inversion charge density, and a low voltage of the charge density. The effect that a thin film having a good rise can be obtained.

  Hereinafter, an example of an apparatus for carrying out the thin film manufacturing method according to the present invention will be described with reference to a schematic arrangement / configuration diagram of a CVD thin film manufacturing apparatus shown in FIG.

  The CVD thin film manufacturing apparatus shown in FIG. 1 has a reaction chamber 2 connected to an evacuation system 1 via a pressure regulating valve 1a, and a shower plate 3 as a gas introduction means provided at an upper portion of the reaction chamber with a predetermined length. A gas mixer 5 connected by a film forming gas pipe 4 and a vaporizer 7 which is a vaporization system connected to the mixer 5 by a raw material gas pipe 6.

  In order to keep the vaporized source gas at a temperature at which the vaporized source gas is not liquefied / deposited / deposited on the apparatus components including the gas piping from the vaporizer 7 to the reaction chamber 2, various valves, a mixer, etc. An exchanger is provided. The pipe 6 between the vaporizer 7 and the mixer 5 is provided with a valve V1 and the pipe 8 between the vaporizer 7 and the exhaust system 1 is provided with a valve V2, whereby the vaporizer 7 and the mixer 5. The exhaust system 1 can be shut off. This is because the maintenance cycles of the components of the vaporizer 7, the mixer 5 and the exhaust system 1 are different, so that substances such as moisture that adversely affect film formation due to release to the atmosphere are avoided from adhering to these components. Is the purpose. When maintenance is performed with one component open to the atmosphere, the vacuum can be maintained without releasing the other two components to the atmosphere.

Hereafter, each said component is demonstrated in detail.
The reaction chamber 2 is provided with a substrate stage 2-1 having a substrate heating means for placing a substrate S as a film formation target. A shower plate 3 is formed on the heated substrate. Film gas is introduced. Excess film forming gas not used for the reaction with the substrate S, by-product gas with the film forming gas generated by the reaction with the substrate, and the reactant gas are exhausted by the exhaust system 1. The shower plate 3 is appropriately heated and maintained at a temperature at which the introduced gas does not liquefy / deposit / film-form.

  The shower plate 3 provided in the upper part of the reaction chamber 2 may be provided with a particle trap as a filter for capturing particles present in the film forming gas. This particle trap may be provided immediately before the shower hole of the shower plate, and it is desirable that the particle trap is appropriately adjusted to a temperature at which a specific vaporized source element necessary for the reaction is not attached or trapped.

  Various film forming pressure conditions can be easily accommodated by the pressure regulating valve 1a provided between the exhaust system 1 and the reaction chamber 2.

  The mixer 5 is connected to the vaporizer 7 by a pipe 6 provided with a valve V1, and two gas sources (for example, oxygen or the like) via a valve, a heat exchanger, and a mass flow controller (not shown). Oxidant gas source: a diluted gas source that is an inert gas such as nitrogen). The film-forming gas obtained by being uniformly mixed in the mixer 5 is introduced into the reaction chamber 2 through the pipe 4 via the shower plate 3, and on the substrate stage 2-1 without becoming a laminar flow in the chamber. It is supplied to the surface of the film-forming target placed.

  In the mixer 5, an appropriately heated oxidizing gas supplied from an oxidizing gas source and a raw material gas that is generated by the vaporizer 7 and sent through a pipe 6 maintained at a temperature at which liquefaction / deposition / film formation is not introduced are introduced. -A film forming gas (oxidizing gas + source gas) is obtained by mixing. This source gas is a gas in which one kind or a plurality of kinds of gases are mixed. The film forming gas thus obtained is introduced into the reaction chamber 2 through the pipe 4.

  The pipes 4 and 6 may be connected by a VCR joint, and the VCR gasket of some of the pipe joints is a VCR type particle trap in which the hole is not a ring but a particle trap. Also good. The joint with this VCR type particle trap is set and maintained at a temperature higher than the temperature at which the source gas is not liquefied / deposited, and does not attach or trap the specific vaporized source elements necessary for the reaction. desirable.

  In the film forming gas pipe 4 between the gas mixer 5 and the shower plate 3, a valve for switching the film forming gas may be provided on the secondary side of the mixer 5. The downstream side of this valve is connected to the reaction chamber 2. During film formation, this valve is opened, and this valve is closed after film formation is completed.

  A raw material supply unit 7 a and a vaporization unit (not shown) are connected to the vaporizer 7. This vaporizer pressurizes and conveys the raw material liquids A, B, and C obtained by dissolving a liquid / solid raw material in an organic solvent with a pressurized gas (for example, an inert gas such as He gas). Each flow rate is controlled by each liquid flow rate controller, and is transported to the vaporization section by the carrier gas.

  The vaporizing section is configured to efficiently vaporize the raw material liquid whose flow rate is controlled and supply the raw material gas obtained by the vaporization to the mixer 5. In this vaporization section, when there is only one liquid raw material, a single liquid can be mixed, and when there are a plurality of liquid raw materials, a plurality of raw material liquids can be mixed and vaporized. When vaporizing the raw material liquid, not only vaporize the liquid droplets of the raw material liquid, but also apply gas to the liquid droplets, apply physical vibrations, or apply ultrasonic waves to the vaporization part wall surface. It is preferable to introduce vaporization into the vaporization part as finer liquid particles through the nozzle and vaporize it to increase the vaporization efficiency. In order to reduce the liquid vaporization load by various particle traps in order to reduce the liquid droplet vaporization as much as possible in the inside of the vaporization part as much as possible at the place where the liquid droplets or liquid particles should be vaporized efficiently. It is preferable to arrange a vaporizing member made of a material having good heat conduction.

  In addition, in order to prevent particles based on the residue generated when the raw material liquid is vaporized from exiting the vaporizer, a small amount of liquid droplets are vacuumed outside the vaporizer. In order to be able to vaporize without being sucked by a particle trap, a particle trap may be provided. In this vaporization member and particle trap, appropriate droplets and fine liquid particles that are in contact with these vaporizers can be properly vaporized, and appropriate vaporizer elements that are necessary for the reaction are not attached or captured. It is desirable that vaporization conditions be maintained at the temperature.

  The vaporizer 7 has a solvent D for dissolving the raw material, and its flow rate is controlled by a flow rate controller so that it can be introduced into the vaporizer and vaporized by the vaporizer, so that this solvent gas can be produced. It may be configured. The inside of the apparatus can be cleaned using this solvent gas.

  As described above, the thin film manufacturing apparatus used in the present invention preferably has a cylindrical reaction chamber 2, and a cylindrical substrate on which a substrate such as a silicon wafer is placed inside the reaction chamber. A stage 2-1 is provided. The substrate stage incorporates a heating means for heating the substrate. Further, the reaction chamber 2 may include means for configuring the substrate stage 2-1 to be movable up and down between the film formation position of the reaction chamber and the substrate transfer position below the reaction chamber. A shower plate 3 is provided in the central portion on the upper side of the reaction chamber 2 so as to face the substrate stage 2-1, so that the film forming gas from which particles are removed is ejected from the shower plate 3 toward the central portion of the substrate. It is configured.

  Incidentally, when a thin film is produced on a substrate by a CVD method such as the MOCVD method, when the source gas is lowered below a certain temperature, the source gas is precipitated as particles, which may cause film formation dust in the reaction chamber. Therefore, a heat exchanger as a gas temperature adjusting means is provided in the oxidizing gas pipe, and a heating means such as a heater is provided on the outer wall of the reaction chamber 2 or the substrate stage 2-1 in order to prevent the deposition of the source gas. It is.

  The film formation temperature at the time of carrying out the thin film production method of the present invention is not particularly limited, and may be a known film formation temperature in a CVD method such as the MOCVD method. For example, the film forming temperature may be about 550 ° C. or less, preferably about 450 to 550 ° C. In the present invention, a thin film composed of two or more layers is manufactured, and the intended purpose is achieved by performing a crystallization annealing treatment at a predetermined temperature. But it can be done.

  Further, this crystallization annealing treatment in the present invention may be performed at a temperature lower than the film forming temperature. For example, when the film formation temperature is 530 ° C., the crystallization annealing treatment is performed at a temperature 110 ° C. lower than the film formation temperature, preferably 80 ° C., more preferably 50 ° C. to a temperature near the film formation temperature. When carried out, satisfactory crystallization is obtained and a thin film having desired electrical characteristics is obtained.

If the thin film manufacturing apparatus shown in FIG. 1 is used, a capacitor electrode film using an organometallic compound containing Pt, Ir, Ru, or the like as a raw material source, for example, Pb (DPM) ₂ , Zr (DMHD) as a liquid raw material ₄ , CVD film formation of the ferroelectric film PZT using Ti (i-PrO) ₂ (DPM) ₂ or the like, CVD film formation in which additive elements such as La, Sr, Ca, Al, etc. are added to this PZT, A high dielectric constant dielectric film BST can be formed by CVD using Ba (DPM) ₂ , Sr (DPM) ₂ , Ti (i-PrO) ₂ (DPM) ₂ or the like as a liquid source, and Cu, Thin films mainly used for metal wiring such as Al, thin films mainly used for barriers such as TiN, TaN, ZrN, VN, NbN, and Al ₂ O ₃ , and other dielectric thin films such as SBT and STO, and this Di, La, Sr, Ca, A The film plus the additive element etc. can be produced by the CVD method.

  In the following examples, a PZT ferroelectric thin film is manufactured by MOCVD using the thin film manufacturing apparatus shown in FIG. 1, and the influence of parameters on the electrical characteristics of the obtained thin film will be described.

  In this example, the dependence of the crystallization annealing temperature on the electrical characteristics of the obtained ferroelectric PZT thin film will be described.

When forming a film using a mixed gas of PZT source gas and oxygen gas (O ₂ ), which is a reaction gas, source material, solvent, reaction gas, carrier gas, substrate, substrate temperature, film formation time, reaction chamber pressure The conditions were as follows.

(Raw material) (Concentration) (Set flow rate)
Pb (thd) ₂ / CHX 0.3mol / L 0.28mL / min
Zr (dmhd) ₄ / CHX 0.3mol / L 0.13mL / min
Ti (i-PrO) ₂ (thd) ₂ / CHX 0.3mol / L 0.20mL / min

Solvent: CHX (cyclohexane)
Reaction gas (O ₂ ) flow rate: 3500sccm
Vaporizer carrier gas (N ₂ ): 300sccm
Substrate: SiO ₂ / Si (8 inch) substrate with Ir electrode oriented in (111) plane orientation Substrate temperature: 530 ° C.
Deposition time: 525 sec
Reaction chamber pressure: 667 Pa

  The film forming pressure was always adjusted to about 667 Pa by a pressure adjusting valve, an inert gas, a reactive gas, or the like. A reaction gas of 1250 sccm was flowed in advance into the reaction chamber, and the pressure was adjusted to the above pressure by APC. The temperature of the reaction chamber, the vaporizer, and each pipe was maintained at 220 ° C. The substrate (wafer) was maintained at 530 ° C. by heating the substrate stage on which it was placed.

Using the apparatus shown in FIG. 1, a PZT thin film was formed as follows.
First, the substrate S is placed in the reaction chamber 2, and containers A, B, and C containing raw material solutions obtained by dissolving the above raw materials in cyclohexane (CHX) 0.3 mol / L, and a container D containing this solvent, respectively. These were pressurized with helium, transported to the vaporizer 7 together with nitrogen as a carrier gas, and vaporized. The raw material gas obtained by vaporization is mixed with oxygen as a reaction gas and nitrogen as a dilution gas in a gas mixer 5, and this mixed gas is passed through a 3/8 inch stainless steel pipe 4 through a shower plate 3. Was introduced into the reaction chamber 2. The introduced mixed gas was transported on a substrate heated to 530 ° C. in the reaction chamber to deposit a PZT thin film. The gas in the reaction chamber 2 was exhausted by the exhaust system 1, and the pressure in the reaction chamber was adjusted to 667 Pa by a pressure regulator. The route from the vaporization system such as a vaporizer other than the substrate stage surface to the exhaust system is a temperature (220 ° C.) at which no precipitation (recrystallization) or decomposition (film formation) of the raw material occurs in the oil circulation system or block heater. Controlled.

  The sample deposited as described above was then subjected to crystallization annealing, upper electrode (TEL) deposition, and subsequent recovery annealing (performed at the same temperature as the crystallization annealing). In this case, the annealing treatment temperature was set to 530 ° C., 500 ° C., 420 ° C., and 350 ° C. Each PZT thin film thus obtained was subjected to X-ray diffraction (XRD) analysis. As a comparison, XRD analysis was also performed on a sample that was not annealed. The obtained XRD spectrum shows that the crystallization of the PZT thin film is promoted as the annealing temperature is increased from 350 ° C. to 530 ° C. Above 420 ° C, no heterogeneous phase (Pyro) was observed, and almost the same crystallization was observed at 500 ° C and 530 ° C.

The leakage current density was measured when a voltage of 2 V was applied to the PZT capacitor using each PZT thin film obtained above. FIG. 2 shows the dependence of the leakage current density (A / cm ² ) on the crystallization annealing treatment temperature. As can be seen from FIG. 2, as the crystallization annealing temperature is increased from 350 ° C. to 420 ° C. and 500 ° C., the leakage current density decreases and then increases slightly to near the film forming temperature. In the annealing temperature range from 420 ° C. to around 530 ° C., the leakage current density was 1.0E-3 A / cm ² or less.

Further, the polarization inversion charge density [QTV characteristics] (Qsw (μC / cm ² )) when a voltage of 0 V to 4.0 V was applied to the PZT capacitor using each PZT thin film obtained above was measured. FIG. 3 shows the dependence of Qsw on the crystallization annealing treatment temperature. In the figure, a: FA 530C, b: FA 500C, c: FA 420C, and FA 350C indicate cases where the annealing temperatures are 530 ° C., 500 ° C., 420 ° C., and 350 ° C., respectively. As is apparent from FIG. 3, Qsw, which is a characteristic of the ferroelectric capacitor, increases as the crystallization annealing treatment temperature is increased, and it is understood that the temperature is almost the same at 500 ° C. and 530 ° C. In the annealing temperature range from 420 ° C. to around 530 ° C., the polarization inversion charge density was 18 μC / cm ² or more when 2 V was applied.

  From the results of the above XRD analysis, leakage current density (FIG. 2), and QTV characteristics (FIG. 3), when the crystallization annealing temperature is set to a temperature range lower than the film formation temperature, for example, the film formation temperature is 530 ° C. In this case, when the temperature is set to 420 ° C. to around 530 ° C., the PZT thin film crystallizes and has excellent electric characteristics.

In this example, in the production of the target thin film, the initial layer and the subsequent bulk layer are divided, and when the initial layer is formed, the flow rate of 0.3M-Pb (thd) ₂ raw material is 0.27 to 0. The film thickness was changed between 29 ml / min, and the bulk layer was formed at a constant flow rate of 0.27 ml / min, and the film forming conditions affecting the electrical characteristics of the PZT thin film The dependence of (the ratio of the raw material gas flow rate in each layer) was examined.

(Table 1)

  In accordance with the above film forming conditions, an initial layer and a bulk layer of a PZT thin film were formed on a substrate (530 ° C.). In any case, crystallization annealing treatment was performed at 500 ° C. after film formation. For the annealed thin film, an upper electrode was formed after analyzing the crystal structure by XRD. Next, a recovery annealing treatment was performed at 500 ° C. to recover damage to the underlying film. With respect to the PZT thin film thus obtained, the XRD spectrum, the leakage current density and the polarization inversion charge density were measured in the same manner as in Example 1.

  FIG. 4 shows an XRD spectrum for studying the dependency of the film formation condition (flow rate of Pb raw material) on crystallization. In FIG. 4, spectra # 1, # 2, and # 3 correspond to the sample numbers in Table 1, respectively. As is apparent from FIG. 4, no heterogeneous phase is observed, and it can be seen that a PZT single phase is obtained in all samples. As for the orientation of the PZT thin film, it can be seen that the larger the Pb raw material flow rate of the initial layer, the more the crystal grows in the (111) direction reflecting the orientation of the substrate.

  As for the sample # 2, the XRD spectrum was measured in the same manner for the thin film obtained by changing the annealing treatment temperature in the same manner as in Example 1. As in the case of Example 1, the annealing treatment temperature was changed. The crystallization was promoted as the value was increased, and the same crystallization tendency was obtained.

Next, FIG. 5 shows the dependence of the film formation condition on the leakage current density when a voltage of 2 V is applied to the PZT capacitor using each PZT thin film obtained above, that is, the initial layer Pb raw material flow rate of the leakage current density. Indicates dependency. As can be seen from FIG. 5, the leakage current density is lower for samples with a lower Pb raw material flow rate in the initial layer. All the samples were 1.0E-4 A / cm ² or less and satisfied the target leakage current density.

  FIG. 6 shows the film formation conditions for the QTV characteristics of the ferroelectric capacitor at each applied voltage when a voltage of 0 V to 4.0 V is applied to the PZT capacitor using each PZT thin film obtained above. Indicates dependency. As apparent from FIG. 6, Qsw greatly depends on the Pb material flow rate at the time of initial layer film formation, and the sample having a larger Pb material flow rate at the time of initial layer film formation has a larger Qsw and rise of Qsw at a low voltage. It turns out that is improving.

  From the above results, a raw material flow rate for obtaining a single-phase PZT thin film having appropriate electrical characteristics was obtained, and a thin film having good QTV characteristics that can be used as a ferroelectric capacitor is a PZT thin film in which the orientation of the substrate is dragged. In order to obtain, it is understood that the Pb material flow rate of the initial layer needs to be equal to or higher than the Pb material flow rate of the bulk layer, preferably more than that flow rate, and that a predetermined annealing process needs to be performed. .

  In this embodiment, the target PZT thin film is divided into an initial layer and a subsequent bulk layer, and when forming each layer, the total film formation time is kept constant, that is, the initial layer and the bulk layer are formed (that is, The film thickness was changed, and the dependence of the film formation time on the electrical characteristics of the PZT thin film was examined. Table 2 shows the film forming conditions. In this case, the Pb material flow rate is slightly different between the initial layer and the bulk layer, but since the film formation rate can be regarded as almost constant, the film thickness can be regarded as being proportional to the film formation time.

(Table 2)

  In accordance with the film formation conditions, an initial layer and a bulk layer of a PZT thin film were formed on the substrate. In any case, crystallization annealing treatment was performed at 500 ° C. after film formation. An upper electrode was formed on the annealed thin film, and then a recovery annealing process was performed at 500 ° C. to recover damage to the underlying film. For the PZT thin film thus obtained, the leakage current density and the polarization inversion charge density were measured in the same manner as in Example 1.

FIG. 7 shows the dependence of the initial layer deposition time (sec) on the leakage current density when a voltage of 2 V is applied to the PZT capacitor using each PZT thin film obtained above. As is clear from FIG. 7, the leakage current density is low in the region where the initial layer deposition time is short, and there is no particular change, but when the initial layer deposition time exceeds 50 seconds (the film thickness is about 10 nm). It can be seen that the leakage current density rises and is about 1.0E-04 A / cm ^{2 in} about 100 seconds.

Further, FIG. 8 shows the dependence on the film formation conditions for the QTV characteristics of the ferroelectric capacitor at each applied voltage when a voltage from 0 V to 4.0 V is applied to the PZT capacitor using each PZT thin film obtained above. Showing gender. In FIG. 8, # 1, # 2, # 3, and # 4 correspond to the sample numbers in Table 2, respectively. As can be seen from FIG. 8, Qsw increases as the initial layer deposition time is increased, and the rise at low voltage is good. Qsw was 25 μC / cm ² or more when 2 V was applied.

From the above results, in order to obtain a PZT thin film that can be used as a ferroelectric capacitor, it is desirable to adjust the film formation time of the initial layer to an optimum range. The deposition time 100sec or less (thickness 20nm or less), preferably if below (thickness 10nm or less) 50 sec, Qsw is 25μC / cm ² or more at 2V applied, preferably to obtain a thin film is 30 .mu.C / cm ² or more be able to. Therefore, if the film thickness of the initial layer is 2 nm to 20 nm, preferably 2 nm to 10 nm, a thin film having the desired electrical characteristics as described above can be obtained. Only thin films with low polarization inversion charge density can be obtained.

  Note that a thin film having desired electrical characteristics can be obtained by making the thickness of the initial layer thinner than the thickness of the second layer, preferably 1/10 or less, more preferably 1/20 or less. However, if it is out of the range, only a thin film having a high leakage current and a low polarization inversion charge density can be obtained.

  According to the present invention, a thin film having excellent electrical characteristics can be obtained by correcting the composition deviation in the initial stage of film formation and controlling the composition in the film thickness direction, and by performing annealing treatment under predetermined conditions after film formation. Therefore, the present invention can be effectively applied to a film forming process by a CVD method in the semiconductor industry where semiconductor elements are highly integrated and have high performance.

The schematic block diagram which shows one structural example of the apparatus for enforcing the thin film manufacturing method concerning this invention. 6 is a graph showing the crystallization annealing temperature dependence of the leakage current density for the capacitor made of the PZT thin film obtained in Example 1. The graph which shows the crystallization annealing temperature dependence of the polarization inversion charge density [QTV characteristic] (Qsw ((micro | micron | mu) C / cm < ² >)) in each applied voltage about the capacitor which consists of a PZT thin film obtained in Example 1. FIG. The XRD spectrum which shows film-forming condition dependence about the PZT thin film obtained in Example 2. FIG. The graph which shows the initial layer Pb raw material flow rate dependence of leakage current density about the PZT thin film obtained in Example 2. FIG. The graph which shows the Pb raw material flow rate dependence of the initial layer of the polarization inversion charge density [QTV characteristic] (Qsw ((micro | micron | mu) C / cm < ² >)) in each applied voltage about the PZT thin film obtained in Example 2. FIG. The graph which shows the initial layer film-forming time dependence with respect to the leakage current density of a ferroelectric capacitor about the PZT thin film obtained in Example 3. FIG. The graph which shows the initial layer film-forming time dependence with respect to Qsw of a ferroelectric capacitor about the PZT thin film obtained in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum exhaust system 1a Pressure adjustment valve 2 Reaction chamber 2-1 Substrate stage 3 Shower plate 4 Film-forming gas piping 5 Gas mixer 6 Raw material gas piping 7 Evaporation system 7a Raw material supply part 8 Piping S Substrate

Claims (24)

  A raw material gas obtained by vaporizing a liquid obtained by dissolving a solid raw material or a liquid raw material in a solvent using a vaporization system, or a film forming gas containing a raw material gas and a reaction gas generated by sublimation from the solid raw material or evaporation from the liquid raw material. In the thin film manufacturing method by the CVD method, which is introduced into the reaction chamber through the introducing means and formed on the substrate heated to the decomposition temperature or higher of the raw material gas, the raw material is produced when a thin film comprising two or more layers is manufactured. An initial layer is formed by introducing a deposition gas containing a source gas having the highest decomposition temperature in the reaction chamber into the reaction chamber in an amount equal to or more than that in the next deposition process, and then the decomposition temperature is the highest. A method for producing a thin film, comprising forming a second layer and subsequent layers by introducing a deposition gas containing a source gas in an amount equal to or less than that of the initial layer deposition process.   In Claim 1, the temperature of the path from the system including the vaporization system to the gas introduction means at the upper part of the reaction chamber is set to a temperature at which the source gas does not precipitate or decompose before reaching the substrate. A thin film manufacturing method characterized in that a film is formed.   A raw material gas obtained by vaporizing a liquid obtained by dissolving a solid raw material or a liquid raw material in a solvent using a vaporization system, or a film forming gas containing a raw material gas and a reaction gas generated by sublimation from the solid raw material or evaporation from the liquid raw material. After the thin film is manufactured according to the thin film manufacturing method by the CVD method, which is introduced into the reaction chamber through the introducing means and formed on the substrate heated to the decomposition temperature of the raw material gas or higher, the film is further formed at a temperature higher than the film forming temperature of the thin film. A thin film manufacturing method characterized by performing a crystallization annealing treatment at a low temperature.   4. When a plurality of source gases are used as source gases in claim 3, the amount of the thin film before the crystallization annealing treatment is equal to or more than the amount of the source gas having the highest decomposition temperature among the source gases in the next film forming process. A film-forming gas containing is introduced into the reaction chamber to form an initial layer, and then a film-forming gas containing the same or lower amount of the source gas having the highest decomposition temperature as that in the case of the initial-layer film forming process is introduced. A thin film manufacturing method, characterized in that it is a thin film in which the second and subsequent layers are formed.   5. The method according to claim 3, wherein (1) the upper electrode is formed after the crystallization annealing treatment, and then the recovery annealing treatment is performed under the same conditions as the crystallization annealing treatment, or (2) before the crystallization annealing treatment. A method of manufacturing a thin film, comprising forming an upper electrode, and then performing an annealing treatment that serves as both a crystallization annealing treatment and a recovery annealing treatment.   6. The thin film manufacturing method according to claim 3, wherein the crystallization annealing treatment is performed in an air atmosphere or an atmosphere having an oxygen concentration higher than that in the air atmosphere.   The crystallization annealing treatment according to any one of claims 3 to 6, wherein the crystallization annealing treatment is performed after the object to be annealed is previously placed in a furnace set at a predetermined temperature and a predetermined atmosphere and held for 30 minutes to 2 hours. A thin film manufacturing method.   8. The thin film manufacturing method according to claim 6, wherein at least one gas selected from oxygen, ozone, dinitrogen monoxide, and mononitrogen dioxide is used in order to make the oxygen concentration higher than that in the air atmosphere. .   9. The thin film manufacturing method according to claim 5, wherein the upper electrode is formed by sputtering.   10. The thin film manufacturing method according to claim 5, wherein the upper electrode is made of a noble metal-based material selected from Pt, Ir, and IrOx.   11. The raw material according to claim 1, wherein the raw material is selected from Pb, Zr, Ti, Ba, Sr, Ta, Bi, La, Ru, Ir, Ni, Mn, Pr, Si, Al, Hf, Mg, and Ca. A thin film manufacturing method comprising at least one element selected from the group consisting of   12. The thin film manufacturing method according to claim 11, wherein the raw material is an organometallic compound as a raw material for MOCVD. 13. The organometallic compound according to claim 12, wherein the organometallic compound is Pb (thd) ₂ ((bis (2,2,6,6) tetramethyl (3,5) heptanedionate) lead), Zr (thd) ₄ ((tetrakis ( 2,2,6,6) tetramethyl (3,5) heptanedionate) zirconium), Zr (dmhd) ₄ ((tetrakis (2,6) dimethyl (3,5) heptanedionate) zirconium), Ti ( i-PrO) ₂ (thd) ₂ ((bisisopropoxide) (bis (2,2,6,6) tetramethyl (3,5) heptanedionate) titanium), Zr (MMP) ₄ ((tetrakis ( 1) methoxy (2) methyl (2) propoxy) zirconium) and Ti (MMP) ₄ ((tetrakis (1) methoxy (2) methyl (2) propoxy) titanium) Thin film manufacturing method.   In any one of Claims 1-10, when using the film-forming gas containing Pb containing source gas as source gas, the film-forming gas which contains this Pb-containing source gas more than the same amount as the following film-forming process is contained in reaction chamber To the initial layer to form a film, and then a film forming gas containing the Pb-containing source gas in an amount equal to or less than that in the initial layer film forming process is introduced to form the second and subsequent layers. A method for producing a thin film. In any one of Claims 1-10, Pb (thd) ₂ , Zr (dmhd) ₄ or Zr (MMP) ₄ and Ti (i-PrO) ₂ (thd) ₂ or Ti (MMP) ₄ are used as source gas. When a Pb (Zr, Ti) O ₃ thin film is manufactured using a film forming gas containing a gas consisting of the above, when the film forming gas made of these raw materials is introduced into the reaction chamber to manufacture the thin film, A deposition gas containing the same amount or more of the source gas as in the next deposition process is introduced into the reaction chamber to form an initial layer, and then this Pb-containing source gas is used in the initial layer deposition process. A method for producing a thin film, wherein a film forming gas containing the same amount or less is introduced to form a second layer and subsequent layers.   16. The method of manufacturing a thin film according to claim 1, wherein the film is formed so that the thickness of the initial layer is thinner than the thickness of the second layer.   17. The method of manufacturing a thin film according to claim 16, wherein the thickness of the initial layer is set to 1/10 (20) or less of the thickness of the second layer.   The method of manufacturing a thin film according to claim 16 or 17, wherein the initial layer has a thickness of 10 (20) nm or less.   19. The method for producing a thin film according to claim 1, wherein at least one solvent selected from tetrahydrofuran, cyclohexane, ethylcyclohexane, and methylcyclohexane is used as a solvent for dissolving the raw material. In any one of claims 1 to 19, as the _{substrate, Pt, Ir, Rh, Ru} , MgO, SrTiO 3, IrO 2, RuO 2, SrRuO 3, and selected from LaNiO _3, the material oriented in a certain plane orientation A method for producing a thin film, comprising using a substrate comprising: In any one of claims 1 to 19, as a _{substrate, Ir / SiO 2 / Si,} Ir / Ti / SiO 2 / Si, Pt / Ti / SiO 2 / Si, and _{SrRuO 3 / Pt / Ti / SiO} 2 / Si A method for producing a thin film, comprising using a material selected from the group consisting of: The thin film to be manufactured according to any one of claims 1 to 21, wherein the thin film to be manufactured is a paraelectric dielectric oxide selected from (Ba, Sr) TiO ₂ and SrTiO ₃ , Pb (Zr, Ti) O ₃ , SrBi ₂ Ta ₂ O. ₉ , and a ferroelectric oxide selected from Bi ₄ Ti ₃ O _12, an electrically conductive oxide selected from SrRuO ₃ and LaNiO _3, from (La, Sr) MnO ₃ and (Pr, Ca) MnO ₃ A method for producing a thin film, which is a thin film of a selected ferromagnetic oxide. 23. The thin film manufacturing method according to claim 22, wherein the Pb (Zr, Ti) O ₃ further contains at least one selected from Nb, La, Ca, and Sr. In any one of claims 3,5～13, and 16 to 21, the thin film to be _{produced, SiO 2, TiO 2, Al} 2 O 3, Ta 2 O 5, MgO, ZrO 2, and selected from HfO ₂ A method for producing a thin film, which is a thin film of an electrically conductive oxide selected from a paraelectric dielectric oxide, IrO ₂ and RuO ₂ .

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