Method of manufacturing semiconductor device and method of forming metal oxide film

A method of manufacturing a semiconductor device having a metal oxide film with workpiece accommodated in a chamber, includes: supplying a precursor gas containing a metal complex into the chamber to form a precursor layer on the workpiece from the precursor gas; supplying an oxidizing gas into the chamber to oxidize the precursor layer so that a metal oxide layer is formed, the oxidizing gas being a gas containing H2O or a gas having a functional group containing hydrogen atoms in the metal complex and containing an oxidant to generate H2O by reaction with the functional group; supplying an H2O removal gas containing alcohols or amines into the chamber to remove H2O adsorbed onto the metal oxide layer; and executing a plurality of cycles each including the supplying a precursor gas and the supplying an oxidizing gas. At least some of the cycles includes the supplying an H2O removal gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application Nos. 2017-133691 and 2018-083356, filed on Jul. 7, 2017 and Apr. 24, 2018, respectively, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a semiconductor device manufacturing method and a metal oxide film forming method.

BACKGROUND

In recent years, a high dielectric constant insulating film (high-K insulating film) has been used as a gate insulating film and a capacitor insulating film in a semiconductor device. As such a high dielectric constant insulating film, for example, an insulating film made of metal oxide having a high dielectric constant, such as HfO2, is known.

In a semiconductor device, in order to secure a channel length in a transistor, increase the capacitance of a capacitor or the like, a trench is formed in a surface of a semiconductor substrate and metal oxide films (a gate insulating film and a capacitor insulating film) are formed on the surface in which the trench is formed. To this end, it becomes important to form a conformal metal oxide film with good step coverage.

In this connection, as a method of forming a metal oxide film, a chemical vapor deposition (CVD) method, an atomic layer deposition (ALD) method and the like are known. Among these, the ALD method has attracted attention since it can obtain a conformal metal oxide film. The term “conformal” used herein means that followability to the shape of a surface to be processed (surface on which a metal oxide film is formed) of a workpiece to be processed by the ALD method is excellent and the metal oxide film has an even thickness distribution.

As one example of a method of forming a metal oxide film using the ALD method, there has been used a method of forming a film made of HfO2by forming a precursor layer on a substrate using tetrakis(dimethylamino)hafnium (TDMAH) as a precursor, followed by oxidizing the precursor layer with H2O.

However, the conventional method fails to obtain a conformal metal oxide film when a process (ALD process) of forming a metal oxide film is performed under low temperature conditions.

SUMMARY

Some embodiments of the present disclosure provide a metal oxide film forming method, which is capable of forming a conformal metal oxide film even under low temperature conditions, and a semiconductor device manufacturing method using the metal oxide film forming method.

According to one embodiment of the present disclosure, there is provided a method of manufacturing a semiconductor device having a metal oxide film in a state in which a workpiece is accommodated in a chamber, the method including: supplying a precursor gas containing a metal complex into the chamber to form a precursor layer on the workpiece from the precursor gas; supplying an oxidizing gas into the chamber to oxidize the precursor layer so that a metal oxide layer is formed, the oxidizing gas being a gas containing H2O or a gas having a functional group containing hydrogen atoms in the metal complex and containing an oxidant to generate the H2O by reaction with the functional group; supplying an H2O removal gas containing alcohols or amines into the chamber to remove the H2O adsorbed onto the metal oxide layer; and executing a plurality of cycles each including the supplying a precursor gas and the supplying an oxidizing gas, wherein at least some of the plurality of cycles includes the supplying an H2O removal gas.

According to another embodiment of the present disclosure, there is provided a method of forming a metal oxide film on a workpiece by an atomic layer deposition technique in a state in which the workpiece is accommodated in a chamber, the method including: supplying a precursor gas containing a metal complex into the chamber to form a precursor layer on the workpiece from the precursor gas; supplying an oxidizing gas into the chamber to oxidize the precursor layer so that a metal oxide layer is formed, the oxidizing gas being a gas containing H2O or a gas having a functional group containing hydrogen atoms in the metal complex and containing an oxidant to generate the H2O by reaction with the functional group; supplying an H2O removal gas containing alcohols or amines into the chamber to remove the H2O adsorbed onto the metal oxide layer; and executing a plurality of cycles each including the supplying a precursor gas and the supplying an oxidizing gas, wherein at least some of the plurality of cycles includes the supplying an H2O removal gas.

DETAILED DESCRIPTION

The present inventors have found that some of H2O used as an oxidant in an ALD method may be adsorbed onto a metal oxide layer by hydrogen bonding and that H2O adsorbed onto the metal oxide layer may stay on the metal oxide layer without being removed at a low process temperature. The present inventors have presumed that the self-limiting property peculiar to the ALD method deteriorates due to such H2O, which may make it impossible to achieve a conformal metal oxide film. That is to say, when a precursor layer is formed on the metal oxide layer, the H2O reacts (hydrolysis reaction) with a metal complex as a precursor, thereby causing an exchange between ligands of the metal complex to generate a precursor having a hydroxyl group (OH group). Since an OH group in this precursor has the same reactivity as an OH group formed on the surface of a workpiece to be processed, the precursor after the ligand exchange reacts with the precursor constituting the precursor layer. In this way, the present inventors have presumed that the self-limiting property deteriorates due to further precursor deposition occurring on the precursor layer, which may make it impossible to achieve a conformal metal oxide film.

Therefore, the present inventors have examined oxidation of the precursor layer using an oxidant such as O3instead of H2O. However, even with this method, it has been found that a conformal metal oxide film cannot be achieved when the metal complex has a functional group containing hydrogen atoms. It is presumed that this is because H2O is by-produced due to extraction of hydrogen atoms in the functional group of the metal complex by the oxidant and the self-limiting property deteriorates due to the by-produced H2O.

As a result of further examination based on the above findings, the present inventors have found that the H2O adsorbed onto the metal oxide layer can be removed by introducing a specific gas into a chamber before a precursor gas is supplied after the metal oxide layer is formed and that further deposition of the precursor on the precursor layer is suppressed in a subsequent step of supplying the precursor gas, thus completing the present disclosure.

FIG. 1is a flowchart showing a metal oxide film forming method according to one embodiment. A method MT shown inFIG. 1is a method of forming a metal oxide film on a workpiece using an atomic layer deposition method. The method MT is executed in a state where the workpiece is accommodated in a chamber. The method MT includes a step S0of accommodating the workpiece in a chamber, a step S1of supplying a precursor gas containing a metal complex into the chamber, a step S2of supplying a purge gas into the chamber, a step S3of supplying an oxidizing gas into the chamber, a step S4of supplying a purge gas into the chamber, a step S5of supplying an H2O removal gas containing alcohols or amines into the chamber, a step SJ1of determining whether to terminate the method MT, and a step SJ2of determining whether to execute step S5.

In the method MT, a plurality of cycles each including step S1, step S2, step S3and step S4is executed. Specifically, a sequence of steps S1to S4is first executed in this order, and step SJ1is then executed. In step SJ1, it is determined whether to terminate the execution of the plurality of cycles. That is to say, if the cycles have not been executed plural times or a predetermined number of times, the result of the determination in step SJ1is NO. When the result of the determination in step SJ1is NO, step SJ2is executed. In step SJ2, it is determined whether to execute step S5. At least some of the plurality of cycles includes step S5. If the result of the determination in step SJ2is YES, step S5is executed and then the cycle is repeated again. If the result of the determination in step SJ2is NO, the cycle is repeated again without executing step S5.

In the method MT, from the viewpoint of improving throughput, the purge gas may not be supplied into the chamber before step S1is executed again after step S5is executed.

Step S5is an arbitrary step in each cycle. However, step S5may be executed in order to obtain a more conformal metal oxide film. However, from the viewpoint of improving throughput, the final cycle of the plurality of cycles in the method MT may not include step S5. If the final cycle does not include step S5, step S4is executed between step S3and step S1in a subsequent cycle. In a case of terminating the method MT after step S3, step S4is executed between step S3and the termination of the method MT.

In the method MT described above, after a first metal oxide layer is formed in a first cycle, a second metal oxide layer is formed on the first metal oxide layer in a subsequent cycle. In this manner, by repeatedly executing a plurality of cycles, a metal oxide film composed of a plurality of metal oxide layers is obtained. The number of repetitions of cycle in the method MT may be appropriately set so as to obtain the oxide film having an intended thickness.

Hereinafter, the details of steps S0to S5in the method MT will be described with reference toFIG. 2. The contents of steps S1to S5in one cycle may be the same as or different from the contents of steps S1to S5in other cycles.

FIG. 2is a schematic cross-sectional view illustrating a film forming apparatus used in the metal oxide film forming method according to one embodiment. InFIG. 2, an arrow indicates a direction of supply of a gas (a precursor gas, an oxidizing gas, an H2O removal gas, a purge gas or the like). The film forming apparatus (ALD film forming apparatus)1includes a chamber body2, a stage4, a gas supply part5and an exhaust device6. An internal space of the chamber body2is defined as a chamber7. The stage4is installed inside the chamber7. The stage4is configured to support a workpiece3disposed thereon. The gas supply part5and the exhaust device6are installed outside the chamber body2and are connected to the chamber body2. The gas supply part5is configured to supply the plural kinds of gases to be used in the method MT into the chamber7. The exhaust device6includes one or more pumps such as a turbo molecular pump and a dry pump, and a pressure control valve, and is configured to exhaust an interior of the chamber7. Although a single supply part5and a single exhaust device6are illustrated inFIG. 2, a plurality of gas supply parts and a plurality of exhaust devices may be used.

In step S0, the workpiece3is disposed on the stage4. A base material (e.g., a substrate) to which the ALD method can be applied can be widely used as the workpiece3. The base material to which the ALD method can be applied is, for example, a semiconductor substrate made of silicon or the like. Examples of such a workpiece may include a semiconductor substrate used to manufacture a semiconductor device having a capacitor insulating film, a semiconductor substrate used to manufacture a semiconductor device having a gate insulating film, and the like.

In step S1, a metal complex in a precursor gas is chemically adsorbed onto the workpiece3to form a precursor layer from the precursor gas. Specifically, when the precursor gas is supplied from the gas supply part5into the chamber7, the precursor gas comes into contact with a surface (surface to be processed) of the workpiece3, so that the metal complex is chemically adsorbed onto the surface of the workpiece3. That is to say, metal atoms in the metal complex react with a functional group such as a hydroxyl group formed on the surface of the workpiece3so that the metal complex (precursor) is chemically adsorbed onto the surface of the workpiece3. This results in formation of a precursor layer composed of a plurality of precursors that is bonded to the surface of the workpiece3. Typically, since ligands are not exchanged between metal complexes, only one molecule of the metal complex is chemically adsorbed but metal atoms are not further deposited in a direction perpendicular to the surface of the workpiece3. Therefore, in step S1, a precursor layer having a uniform thickness is obtained. The term “precursor gas” used herein means a gas composed of a precursor containing a metal complex. Although a precursor before being chemisorbed onto the workpiece is different in terms of structure from a precursor after being chemisorbed onto the workpiece, these precursors will be hereinafter collectively referred to as a precursor for the sake of convenience in description.

In step S1, various metal complexes may be used depending on the type of metal constituting a target metal oxide film. Any metal complex may be used as long as it can be chemically adsorbed onto the surface of the workpiece3. The metal complex is represented, for example, by the following chemical formula (1).

In the chemical formula 1, M represents a central metal, and L1to L4represent ligands independently. L1to L4may be the same as or different from each other.

The central metal may be hafnium, zirconium, aluminum, tantalum, tungsten, titanium, niobium, molybdenum, cobalt, nickel or the like. That is to say, the metal complex may be a hafnium complex, a zirconium complex, an aluminum complex, a tantalum complex, a tungsten complex, a titanium complex, a niobium complex, a molybdenum complex, a cobalt complex, a nickel complex or the like. From the viewpoint of obtaining a metal oxide film having a high dielectric constant, the metal complex may be a hafnium complex, a zirconium complex, an aluminum complex, a tantalum complex or a tungsten complex.

Examples of the ligands may include alcohols such as t-butylalcohol, isopropylalcohol, isobutylalcohol and the like, amines such as dimethylamine, ethylmethylamine, diethylamine, t-butylamine and the like, cyclopentadiene, butadiene, benzene, and the like.

The ligands may have a functional group containing hydrogen atoms. When the ligands have a functional group containing hydrogen atoms, an oxidant in an oxidizing gas supplied in step S3to be described later may react with the functional group to produce H2O. Therefore, when the ligands have a functional group containing hydrogen atoms and the oxidizing gas is a gas containing an oxidant which reacts with the functional group to produce H2O, the effects of the present disclosure are remarkably exhibited. An example of the functional group containing hydrogen atoms may include a hydrocarbon group.

Examples of the metal complex may include Hf[N(CH3)2]4, Hf[N(CH2CH3)(CH3)]4, Hf[N(CH3)2]3[C5H5], Hf[N(CH2CH3)3]4and Hf[OC(CH3)3]4. Among these, at least one selected from a group consisting of Hf[N(CH3)2]4, Hf[N(CH2CH3)(CH3)]4and Hf[N(CH3)2]3[C5H5] may be used to ensure a vapor pressure.

The conditions for supplying the precursor gas in step S1are not particularly limited but may be conventionally known conditions for forming a precursor layer using the ALD method. However, when an internal temperature of the chamber7is high, decomposition of the precursor (for example, cleavage of the bond between the workpiece and the precursor, desorption of the ligands, etc.) occurs, which may make it difficult to obtain a conformal metal oxide film. Further, with the refinement of a semiconductor substrate or the like serving as a workpiece, a low temperature process is required. Therefore, the internal temperature of the chamber7when the precursor gas is supplied into the chamber7may be 700 degrees C. or lower. The internal temperature of the chamber7when the precursor gas is supplied into the chamber7may be, for example, 100 degrees C. or higher. The internal pressure of the chamber7when the precursor gas is supplied into the chamber7may be, for example, 10 Pa or more and may be 50,000 Pa or less. The supply amount (supply time and flow rate) of the precursor gas may be adjusted according to the size or the like of the workpiece. The supply amount of the precursor gas may be, for example, 0.1 sccm or more and may be 1,000 sccm or less. In step S1, the precursor gas may be continuously supplied in the form of a pulse so that all OH groups on the surface of the workpiece3react with the metal complex.

The supply of the precursor gas may be performed under a dilution gas (first dilution gas) environment. For example, the precursor gas may be supplied after replacing the interior of the chamber7with the first dilution gas. In addition, the first dilution gas may be supplied into the chamber7, for example together with the precursor gas. In this case, the precursor gas may be supplied while supplying the first dilution gas into the chamber7. Alternatively, the precursor gas and the first dilution gas may be mixed and the precursor gas (mixed gas) diluted with the first dilution gas may be supplied into the chamber7. Examples of the first dilution gas may include a nitrogen (N2) gas, an inert gas such as a noble gas, a carbon dioxide (CO2) gas and a carbon monoxide (CO) gas. The first dilution gas may include at least one selected from a group consisting of a helium (He) gas, a neon (Ne) gas, an argon (Ar) gas, a krypton (Kr) gas, a xenon (Xe) gas, an N2gas, a CO2gas and a CO gas.

In step S2, the precursor gas is removed from the chamber7by the purge gas. Specifically, when the purge gas is supplied from the gas supply part5into the chamber7, the precursor gas in the chamber7is removed, together with the purge gas, from the chamber7by the exhaust device6. Examples of the purge gas may include an inert gas such as a nitrogen gas, a noble gas (for example, an argon gas, etc.) or the like, a carbon dioxide gas and a carbon monoxide gas. Gases corresponding to the precursor gas, the oxidizing gas and the H2O removal gas are not included in the purge gas. The conditions for supplying the purge gas in step S2are not particularly limited but may be 700 degrees or lower from the viewpoint of suppressing the decomposition of the precursor and reducing a thermal damage to the workpiece. The internal temperature of the chamber7when the purge gas is supplied into the chamber7may be, for example, 100 degrees C. or higher. An internal pressure of the chamber7when the purge gas is supplied into the chamber7may be, for example, 10 Pa or more and may be 50,000 Pa or less. The supply amount (supply time and flow rate) of the purge gas may be appropriately set so that the precursor gas is completely removed. The supply amount of the purge gas may be, for example, 0.1 sccm or more and may be 1,000 sccm or less.

In step S3, the precursor layer is oxidized by the oxidizing gas to form a metal oxide layer. Specifically, when the oxidizing gas is supplied from the gas supply part5into the chamber7, the oxidant in the oxidizing gas comes into contact with the precursor layer and the precursor constituting the precursor layer reacts with the oxidant. As a result, the precursor is oxidized to form a metal oxide layer composed of metal oxide. At this time, the ligands are desorbed from the precursor.

The oxidizing gas is a gas containing H2O (for example, an H2O gas), or a gas containing an oxidant that reacts with a functional group containing hydrogen atoms of the metal complex to generate H2O (for example, a gas of an oxidant that reacts with a functional group containing hydrogen atoms of the metal complex to generate H2O). A gas corresponding to the H2O removal gas is not included in the oxidizing gas. Examples of the oxidant that reacts with a functional group containing hydrogen atoms of the metal complex to form H2O may include O3, H2/O2mixture, O2plasma, O2, H2O2and the like. When a gas containing H2O is used as the oxidizing gas, H2O derived from the oxidizing gas is adsorbed onto the metal oxide film by hydrogen bonding. When a gas containing an oxidant such as O3, H2/O2mixture, O2plasma, O2, H2O2and the like is used as the oxidizing gas, H2O derived from the reaction between the oxidant and the functional group containing hydrogen atoms of the metal complex is adsorbed onto the oxide film by hydrogen bonding. From the viewpoint of forming a metal oxide layer under the low temperature conditions, the oxidizing gas may be a gas containing at least one selected from a group consisting of O3, H2/O2mixture, O2plasma, O2and H2O2, specifically a gas containing at least one selected from a group consisting of O3, H2/O2mixture and O2plasma.

The conditions for supplying the oxidizing gas in step S3are not particularly limited but the internal temperature of the chamber7when the oxidizing gas is supplied into the chamber7may be 700 degrees or lower from the viewpoint of maintaining the bonding between the metal in the precursor layer and the metal oxide layer and the surface to be processed and from the viewpoint of reducing a thermal damage to the workpiece3. The internal temperature of the chamber7when the oxidizing gas is supplied into the chamber7may be, for example, 100 degrees C. or higher. The internal pressure of the chamber7when the oxidizing gas is supplied into the chamber7may be, for example, 10 Pa or more and may be 50,000 Pa or less. The supply amount (supply time and flow rate) of the oxidizing gas may be appropriately set so that the precursor constituting the precursor layer is completely oxidized. The supply amount of the oxidizing gas may be, for example, 0.1 sccm or more and may be 1,000 sccm or less.

The supply of the oxidizing gas may be performed under a dilution gas (second dilution gas) environment. For example, the oxidizing gas may be supplied after replacing the interior of the chamber7with the second dilution gas. In addition, the second dilution gas may be supplied into the chamber7, for example together with the oxidizing gas. In this case, the oxidizing gas may be supplied while supplying the second dilution gas into the chamber7. Alternatively, the oxidizing gas and the second dilution gas may be mixed and the oxidizing gas (mixed gas) diluted with the second dilution gas may be supplied into the chamber7. The details of the second dilution gas are the same as those of the above-described first dilution gas.

In step S4, when the purge gas is supplied from the gas supply part5into the chamber7, the oxidizing gas and the ligands derived from the precursor are removed from the chamber7by the exhaust device6. The details of the purge gas and the conditions for supplying the purge gas in step S4may be the same as those in the above-described step S2.

In step S5, H2O adsorbed onto the metal oxide layer is removed by the H2O removal gas. Specifically, when the H2O removal gas is supplied from the gas supply part5into the chamber7, the H2O removal gas comes into contact with the metal oxide layer, so that H2O adsorbed onto the metal oxide layer is substituted with alcohols or amines in the H2O removal gas. As a result, H2O is desorbed from the surface of the metal oxide layer. The desorbed H2O is removed from the chamber7by continuously supplying the H2O removal gas.

The likelihood of substitution of H2O in step S5can be predicted, for example, by evaluating the energy of adsorption of a substituted compound (e.g., alcohols and amines) onto the surface (surface site) of the metal oxide layer. That is to say, when the energy of adsorption of the substituted compound onto the surface (surface site) of the metal oxide layer is larger than the energy of adsorption of H2O onto the surface (surface site) of the metal oxide layer, it is predicted that H2O is easily substituted with the substituted compound. Alcohols and amines have high polarity and exhibit the energy of adsorption higher than H2O on the surface site of the metal oxide layer. Therefore, in the present embodiment, the alcohols or amines and the H2O adsorbed onto the metal oxide layer interfere with each other on the surface site. As a result, it is inferred that H2O is substituted with alcohols or amines with a certain probability and is desorbed from the surface of the metal oxide layer. The adsorption energy can be obtained, for example, by a density functional formalism (PBE/DN) using a DMol3module of Software Materials Studio.

Alcohols or amines adsorbed onto the metal oxide layer can react with the metal complex which is a precursor, when step S1is performed again, like H2O, but do not react with other precursors due to steric hindrance. Therefore, in the present embodiment, deposition of two or more precursors, which is a concern in the conventional ALD method, hardly occurs. That is to say, in the present embodiment, by executing step S5, it is possible to maintain the self-limiting property peculiar to ALD to obtain a conformal metal oxide film.

The H2O removal gas contains at least one of the alcohols and the amines and may contain both the alcohols and the amines.

The alcohols is an alcohol compound represented by the formula R1OH (where, R1represents a monovalent hydrocarbon group) and the amines is an amine compound represented by the formula R2R3R4—N(where, R2, R3and R4represent a hydrogen atom or a monovalent hydrocarbon group and at least one of R2, R3and R4represents a monovalent hydrocarbon group. R2, R3and R4may be the same as or different from each other.). The number of carbons in R1, R2, R3and R4may be, for example, 1 to 8. The hydrocarbon groups of R1, R2, R3and R4may be either linear, branched or cyclic and may be either saturated or unsaturated. R1, R2, R3and R4may have a substituent group as long as it does not inhibit the effects of the present disclosure. Specific examples of R1, R2, R3and R4may include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group and an isobutyl group, an allyl group, a phenyl group and the like.

Specific examples of the alcohols may include alkyl alcohols such as methyl alcohol (methanol), ethyl alcohol (ethanol), n-propyl alcohol (1-propanol), isopropyl alcohol (2-propanol), t-butyl alcohol (2-methyl-2-propanol), isobutyl alcohol (2-methyl-1-propanol) and the like, allyl alcohols, phenol and the like. Among these, at least one selected from a group consisting of methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and t-butyl alcohol may be used from the viewpoint of easy removal of H2O adsorbed onto the metal oxide.

Specific examples of the amines may include diethylamine, methylamine, ethylamine, isopropylamine, aniline and the like. Among these, at least one selected from a group consisting of diethylamine, ethylamine and methylamine may be used from the viewpoint of easy removal of H2O adsorbed onto the metal oxide.

The conditions for supplying the H2O removal gas in step S5are not particularly limited but the internal temperature of the chamber7when the H2O removal gas is supplied into the chamber7may be 700 degrees or lower from the viewpoint of maintaining the bonding between the metal in the metal oxide layer and the surface to be processed and from the viewpoint of reducing a thermal damage to the workpiece. The internal temperature of the chamber7when the H2O removal gas is supplied into the chamber7may be, for example, 100 degrees C. or higher. The internal pressure of the chamber7when the H2O removal gas is supplied into the chamber7may be, for example, 10 Pa or more and may be 50,000 Pa or less. The supply amount (supply time and flow rate) of the H2O removal gas may be appropriately set so that all H2O adsorbed onto the metal oxide layer by hydrogen bonding is completely removed. The supply amount of the H2O removal gas may be, for example, 0.1 sccm or more and may be 1,000 sccm or less.

The supply of the H2O removal gas may be performed under a dilution gas (third dilution gas) environment. For example, the H2O removal gas may be supplied after replacing the interior of the chamber7with the third dilution gas. In addition, the third dilution gas may be supplied into the chamber7, for example together with the H2O removal gas. In this case, the H2O removal gas may be supplied while supplying the third dilution gas into the chamber7. Alternatively, the H2O removal gas and the third dilution gas may be mixed and the H2O removal gas (mixed gas) diluted with the third dilution gas may be supplied into the chamber7. The details of the third dilution gas are the same as those of the above-described first dilution gas.

The above-described method MT can be suitably used to form a gate insulating film and a capacitor insulating film, for example. Particularly, in a semiconductor device having a memory cell such as 3DNAND, DRAM or the like, a step coverage of an insulating film becomes an important issue with the complication of a trench structure and an increase in aspect ratio of the trench, and the like. Thus, it is possible to form an ideal conformal film with high step coverage and low loading effects according to the above-described method MT.

Since the method MT can be carried out under the low temperature conditions, according to the method MT, it is possible to form a conformal metal oxide film even under the low temperature conditions. Further, by applying the method MT to a semiconductor device manufacturing method, it is possible to form a conformal insulating film (a capacitor insulating film, a gate insulating film and the like) while reducing a thermal damage to a semiconductor substrate in a process of forming the metal oxide film such as the capacitor insulating film, the gate insulating film and the like. That is to say, according to the method MT, it is possible to achieve a semiconductor device having a conformal insulating film (a capacitor insulating film, a gate insulating film and the like).

Next, the semiconductor device manufacturing method using the above-described method MT will be described with reference toFIGS. 3A to 3CandFIGS. 4A to 4C.

FIGS. 3A to 3Care schematic cross-sectional views showing the semiconductor device manufacturing method according to one embodiment. The manufacturing method of the present embodiment involves manufacturing a semiconductor device having a capacitor insulating film. In the manufacturing method of the present embodiment, first, as shown inFIG. 3A, a semiconductor substrate11is prepared as a workpiece. The semiconductor substrate11includes a substrate12, a first electrode (plate electrode)13, an oxide film14and a nitride film15. The substrate12is made of a material containing silicon (Si), such as silicon nitride. The oxide film14is formed on the substrate12and the nitride film15is formed on the oxide film14. Some trenches16are formed in a laminate including the substrate12, the oxide film14and the nitride film15. A partial region of the substrate12extending along the trenches16constitutes the first electrode13. The first electrode13contains a dopant such as arsenic (As), phosphorus (P) or the like.

In the present embodiment, the surface of the semiconductor substrate11is a surface (surface to be processed) on which a metal oxide film is formed. The semiconductor substrate11is obtained by the following method, for example. First, the oxide film14and the nitride film15are sequentially formed on the substrate12. Subsequently, the trenches16are formed in the laminate including the substrate12, the oxide film14and the nitride film15by etching or the like. Thereafter, a dopant is implanted into the partial region of the substrate12along the trenches16by a method such as gas phase diffusion to form the first electrode13. Through the above process, the semiconductor substrate11is obtained. Subsequently, as shown inFIG. 3B, by applying the metal oxide film forming method of this embodiment to the surface to be processed of the semiconductor substrate11, a capacitor insulating film17formed of a metal oxide film is formed on the semiconductor substrate11. Subsequently, as shown inFIG. 3C, a second electrode (node electrode)18is formed on the capacitor insulating film17. The second electrode18is made of, for example, amorphous silicon, polysilicon or the like containing impurities of a predetermined conductivity type. Through the above process, it is possible to achieve a semiconductor device19having a conformal capacitor insulating film17with excellent step coverage.

A shape and size (width, depth, etc.) of the trenches16in the semiconductor substrate11are not particularly limited. The depth of the trenches16may be, for example, 0.1 to 10 μm. The width of the trenches16may be 5 to 500 nm. The aspect ratio (trench depth/trench width) of the trenches16may be, for example, 0.2 to 80. According to the method of the present embodiment, even when the aspect ratio of the trenches16is large (for example, 80 or more), it is possible to achieve excellent step coverage.

A thickness of the capacitor insulating film17may be, for example, 1 Å or more and may be 10,000 Å or less.

FIGS. 4A to 4Care schematic cross-sectional views showing a semiconductor device manufacturing method according to another embodiment. The manufacturing method of this embodiment involves manufacturing a semiconductor device having a gate insulating film. In the manufacturing method of this embodiment, first, as shown inFIG. 4A, a semiconductor substrate21is prepared as a workpiece. The semiconductor substrate21includes an oxide insulating film22, an oxide semiconductor film23, a first electrode (source electrode)24and a second electrode (drain electrode)25. The oxide insulating film22is formed on a substrate made of silicon or the like (for example, a semiconductor substrate, not shown). The oxide semiconductor film23is formed on the oxide insulating film22. A laminate including the oxide insulating film22and the oxide semiconductor film23provides a trench26. Specifically, the trench26is defined by a surface of the oxide semiconductor film23. The first electrode24and the second electrode25are formed on the oxide semiconductor film23. The first electrode24and the second electrode25are located at both sides of the trench26, respectively.

In this embodiment, the surface defining the trench26of the semiconductor substrate21is a surface (surface to be processed) on which a metal oxide film is formed. The semiconductor substrate21is obtained by the following method, for example. First, the oxide insulating film22made of silicon or the like is formed on the substrate by a sputtering method or the like. Subsequently, the surface of the oxide insulating film22is etched to form the trench26and then the oxide semiconductor film23is formed on the surface of the oxide insulating film22by a sputtering method or the like. Finally, a conductive film made of a conductive material such as Al is formed on the oxide semiconductor film23. Thereafter, the conductive film is etched by photolithography or the like to form the first electrode24and the second electrode25. Through the above process, the semiconductor substrate21is obtained. Subsequently, as shown inFIG. 4B, by applying the metal oxide film forming method of this embodiment to a surface to be processed of the semiconductor substrate21, a gate insulating film27formed of a metal oxide film is formed on the semiconductor substrate21. Subsequently, as shown inFIG. 4C, a third electrode (gate electrode)28is formed on the gate insulating film27in the trench26. The third electrode28is made of a conductive material such as indium tin oxide. Through the above process, it is possible to achieve a semiconductor device29having the conformal gate insulating film27with excellent step coverage.

A shape and size (width, depth, etc.) of the trench26in the semiconductor substrate21are not particularly limited. The depth, width and aspect ratio of the trench26may be the same as the depth, width and aspect ratio of the trenches16in the above-described semiconductor substrate11.

A thickness of the gate insulating film27may be, for example, 1 Å or more and may be 10,000 Å or less.

While the metal oxide film forming method and the semiconductor device manufacturing method using the metal oxide film forming method according to an embodiment of the present disclosure have been described above, the present disclosure is not limited to the embodiment.

For example, each cycle may not include step S2and step S4. From the viewpoint of obtaining a more conformal metal oxide film, it is preferable to execute step S2and step S4in each cycle.

In some embodiments, in the metal oxide film forming method, after step S2and step S3are executed, step S2and step S3may be repeated so that the precursor layer is completely oxidized.

In some embodiments, the final cycle of the plurality of cycles may include step S5.

In some embodiments, the metal oxide film forming method may include other steps than the above-described steps as long as they do not hinder the effects of the present disclosure. For example, the metal oxide film forming method may include an additional step of supplying a purge gas into the chamber after step S5is executed and before step S1is executed again. Further, each cycle may include another additional step of evacuating the interior of the chamber between step S1and step S3, in addition to or instead of step S2. By executing the another additional step, it is possible to reliably remove the purge gas from the chamber. Similarly, each cycle may include yet another additional step of evacuating the interior of the chamber between step S3and step S5, in addition to or instead of step S4, or may include still another additional step of evacuating the interior of the chamber, in addition to or instead of step S6, after step S5is executed and before step S1is executed again.

EXAMPLES

Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples.

The DMol3module of Software Materials Studio was used to calculate the energy of adsorption of water (H2O) and methyl alcohol (CH3OH) onto a hafnium oxide (HfO2) substrate according to the density functional method (PBE/DN). The hafnium oxide (HfO2) substrate used was a substrate (with unit cell=2×2×1.5) in which monoclinic hafnium oxide (HfO2) crystal is cut out in the (111) plane to form Hf—OH termination. The adsorption energy was calculated for three adsorption modes of Shallow Adsorption, 1H-Bonded Adsorption and 2H-Bonded Adsorption. The results are shown below.

[Adsorption Energy of H2O]

The adsorption energy in Shallow Adsorption was −0.41 eV, the adsorption energy in 1H-Bonded Adsorption was −0.83 eV and the adsorption energy in 2H-Bonded Adsorption was −1.23 eV.

[Adsorption Energy of CH3OH]

The adsorption energy in Shallow Adsorption was −0.61 eV, the adsorption energy in 1H-Bonded Adsorption was −0.97 eV and the adsorption energy in 2H-Bonded Adsorption was −1.34 eV.

As described above, it was confirmed that CH3OH has higher adsorption energy than H2O with respect to the hafnium oxide substrate.

According to the present disclosure in some embodiments, it is possible to provide a metal oxide film forming method, which is capable of forming a conformal metal oxide film even under low temperature conditions, and a semiconductor device manufacturing method using the same method. In addition, according to the present disclosure in some embodiments, it is possible to form a conformal capacitor insulating film while reducing a thermal damage to a semiconductor substrate in a process of forming a capacitor insulating film. That is to say, a semiconductor device achieved by the method of the present disclosure includes the conformal capacitor insulating film.