Patent Application
20050170665
1. Field of the Invention
The present invention generally relates to a method of forming a semiconductor device, and particularly to a method of forming a high dielectric film of a semiconductor device.
2. Description of the Related Art
Owing to the growing development of technology for miniaturizing the semiconductor device, presently, a super-miniaturized/high speed semiconductor device with a gate length of less than 0.1 μm can be fabricated. In order to realize high speed operation in such a super-miniaturized semiconductor device, the thickness of a gate dielectric film needs to be reduced to 1 nm or less according to the scaling rule. In the case of using a very thin gate dielectric film, a tunnel current may pass through the gate dielectric film causing an increase in the gate leak current.
To counter such a problem, it has been proposed in the prior art to use a so-called high-K dielectric film corresponding to a high dielectric film with a small equivalent oxide thickness (EOT) instead of a silicon oxide film that is conventionally used as a gate dielectric film. The high-K dielectric film may have a relatively thick physical thickness while having a small equivalent electric thickness with respect to a silicon oxide film. It is noted that the high-K dielectric film may correspond to a metal oxide film made of ZrO2, HfO2, or Al2O3 that has a high specific inductive capacity and a wide band gap, a metal silicate film made of ZrSiO4 or HfSiO4, or a metal aluminate film, for example.
The high-K dielectric film may also be used in a DRAM cell having a super-miniaturized memory cell capacitor to prevent an increase of a capacitor leak current by the tunnel current, and secure a sufficient capacitance in the memory cell capacitance, for example.
In the prior art, the high-K dielectric film may be formed through ALD (Atomic Layer Deposition) or MOCVD (Metal Oxide Chemical Vapor Deposition) using an organic metal compound precursor. In ALD, chemical adsorption of organic metal compound molecular precursor is conducted on a substrate to be treated, after which oxidation is conducted on the chemically adsorbed 1˜2 molecular thickness molecular precursor layer using an oxidation agent, and this process is repeatedly conducted to form multiple layers of 1˜2 molecular thickness precursor films to obtain a desired high-K dielectric layer.
As the organic metal compound precursor, amine-based material such as tetrakis(dimethylamino)hafnium (Hf[N(CH3)2]4), tetrakis(diethylamino) hafnium (Hf[N(CH2CH3)2]4), tetrakis(dimethylamino)zirconium (Zr[N(CH3)2]4), and tetrakis(diethylamino)zirconium (Hf[N(CH2CH3)2]4) may be used, for example.
However, these organic metal compounds contain organic functional groups in their molecules, and thereby, a large amount of carbon may remain in the fabricated high-K dielectric film.
Logically speaking, since a Hf—N bond is weaker than a N—C bond, when chemically adsorbed Hf[N(CH3)2]4 molecules are reacted with an oxidation agent such ash H2O, O2, or O3, a desired HfO2 molecular layer is expected to be formed.
In other words, since the N—C bond contained in the organic reactant for realizing oxide reaction is more stable than the Hf—N bond contained in the molecular precursor, it is expected that the desired HfO2 molecular film be formed without leaving carbon behind in the film.
However, as is described above, in the high-K dielectric film formed using the above organic compound precursors, carbon inevitably remains in the film due to the organic functional groups contained within the precursor molecules and as a result, defects are created in the film by the residual carbon. In a case where the residual carbon is removed through oxidation at a later process stage, dangling bonds may be created within the film. A film having such dangling bonds is unstable both from a dynamical perspective and a chemical perspective, and thereby leads to a decrease in reliability of a semiconductor device using such a high-K dielectric film. Also, the dangling bonds may lead to a decrease in the specific inductive capacity of the high-K dielectric film.
For example, in the prior art, when Hf[N(CH3)2]4 and oxygen gas are used as precursors to form a HfO2 film with a thickness of 3˜5 nm on a silicon substrate surface at a substrate temperature of 200˜550° C. by growing the film at a growth rate of a few nanometers per minute (nm/min) under a processing pressure of approximately 133 Pa (1 Torr), the concentration of the residual carbon contained in the film may reach up to 1×1020 cm−3˜1×1021 cm−3 according to research conducted by the inventor of the present invention.
It is noted that a technique is known in the prior art for forming a high-K dielectric film that does not contain residual carbon. According to such a technique, a chloride precursor such as HfCl4 or ZrCl4 is used instead of an organic metal compound precursor. However, when a chloride precursor is used, chloride may remain in the formed high-K dielectric film to cause corrosion in the vicinity of the high-K dielectric film, for example.
It is known that amine-based organic compound materials are characterized by being highly reactive to hydrogen and are capable of inducing precipitation of metal or metal nitride compounds.
For example, in a case where Hf[N(CH3)2]4 and hydrogen gas are combined, metal Hf or HfN may be precipitated by one of the following reactions:
Hf[N(CH3)2]4+2H2→Hf+4H−N(CH3)2 (1)
2Hf[N(CH3)2]4+5H2→2HfN+6H−N(CH3)2+4CH4 (2)
In these reactions, the organic functional group may be desorbed from the metal element in a very efficient manner. Thereby, in forming a high-K dielectric film using an amine-based metal compound precursor, the organic functional groups are expected to be effectively desorbed during the metal molecular precipitation reaction of the surface of the substrate to be treated by doping hydrogen gas to the precursor.
However, it is difficult to control the above reactions (1) and (2), and generally, the reactions tend to occur in gas phase. Thereby, when hydrogen is simply doped into the precursor gas, a large amount of metal powder (particles) may inevitably be created as a result of the volatile reaction occurring within the reaction chamber.
It is a general object of the present invention to provide a method of forming an improved high-K dielectric film and a method of fabricating a semiconductor film using such a high-K dielectric film.
More specifically, it is an object of the present invention to provide a method of forming a high-K dielectric film through MOCVD using an amine-based organic metal compound precursor that is capable of reducing the amount of residual carbon in the high-K dielectric film.
It is another object of the present invention to provide a method of forming a dielectric film using an amine-based organic metal compound precursor, the method including the steps of:
According to an aspect of the present invention, amine-based organic metal compound precursor molecules are adsorbed onto the surface of a substrate in a precursor gas supplying step, and the amine-based organic metal compound precursor molecules are evacuated from the surface of the substrate in a precursor gas evacuating step, after which a hydrogen gas supplying step is conducted so that carbon contained in a resulting metal film formed on the surface of the substrate that is made of a metal element contained in the organic metal precursor molecules may be efficiently removed to thereby obtain a high-K dielectric film that is substantially free of carbon. Then, by conducting an oxidation gas introducing step to realize an oxidation process on the metal film, a desirable dielectric film, particularly a high-K dielectric film, that has a low concentration of carbon and is free of halogen such as chloride may be formed. According to an aspect of the present invention, the amine-based organic metal compound precursor gas that may cause a volatile reaction with the hydrogen gas is removed from the surface of the substrate before the hydrogen supplying step is conducted so that particle generation may be prevented, for example.
FIGS. 8A˜8D are diagrams illustrating process steps of fabricating a high-speed semiconductor device according to a fifth embodiment of the present invention;
FIGS. 9A˜9C are diagrams illustrating process steps of fabricating a MOS capacitor according to a sixth embodiment of the present invention; and
In the following, preferred embodiments of the present invention are described with reference to the accompanying drawings.
The MOSCVD apparatus 10 shown in
Also, it is noted that a shower head 13 made of quartz glass, for example, is provided within the processing space 11A. The shower head 13 is arranged to face against the substrate W being supported by the substrate supporting member 12. The shower head 13 is arranged to receive an organic metal compound precursor gas such as Hf[N(CH3)2]4 (referred to as TDMAH hereinafter) from line L1, an oxidation gas such as H2O from line L2, and a hydrogen gas from L3, the respective gases being supplied to the shower head 13 along a with nitrogen carrier gases.
According to a specific example, TDMAH is stored in a precursor bottle 141, as a liquid precursor. A bubbling process is conducted on the TDMAH in the precursor bottle 141 by a nitrogen gas supplied from line 151 via a mass flow controller (MFC) 15a. The TDMAH gas generated in this manner is supplied to the shower head 13 via line L1 along with a nitrogen carrier gas that is supplied from line 161 via a mass flow controller (MFC) 16a and a valve 17a.
Also, according to the present example, H2O is stored in a precursor bottle 142 as a liquid precursor (i.e., water) A bubbling process is conducted on the H2O in the precursor bottle 142 by a nitrogen gas supplied from line 152 via a mass flow controller (MFC) 15b. The H2O gas generated in this manner is supplied to the shower head 13 via line L2 along with a nitrogen carrier gas that is supplied from line 162 via a mass flow controller (MFC) 16b and a valve 17b.
Also, the hydrogen gas, which is supplied from a gas cylinder (not shown) via line 153 and a mass flow controller 15c, is supplied to the shower head 13 via line L3 along with a nitrogen carrier gas that is supplied from line 163 via a mass flow controller 16c and a valve 17c.
It is noted that the lines L1, L2, and L3 are provided with valves LV1, LV2, and LV3, respectively. Also, a vent valve VV1 is connected to the upstream side of the valve LV1, a vent valve VV2 is connected to the upstream side of the valve LV2, and a vent valve VV3 is connected to the upstream side of the valve LV3.
According to the present example, the MOCVD apparatus 10 of
According to
Then, in step 2, the evacuation valve EV and the vent valve VV1 are closed, and the valve LV1 is opened so that a precursor gas including TDMAH molecules is supplied to the processing space 11A via line L1. As a result, the TDMAH molecules included in the precursor gas are chemically adsorbed onto the surface of the substrate W so that a precursor molecular layer that covers the surface of the substrate is formed.
Then, in step 3, the evacuation valve EV and the vent valves VV1˜VV3 are opened, and the valves LV1˜LV3 are closed so that gas is evacuated from the processing space 11A.
Then, in step 4, the evacuation valve EV and the vent valve VV3 are closed, and the valve LV3 is opened so that hydrogen gas in line 153 is supplied to the processing space 11A. The hydrogen gas supplied to the processing space 11A is typically attenuated to a concentration of around 3% by the nitrogen carrier gas in line 163.
The hydrogen gas supplied to the processing space 11A in the manner described above reacts with the TDMAH molecules adsorbed to the surface of the substrate W, the reaction corresponding to the reaction (1) described above. As a result, organic functional groups containing carbon are removed from the TDMAH molecules, and a layer made of the metal element Hf that covers the surface of the substrate W is formed.
Then, in step 5, the evacuation valve EV and the vent vales VV1˜VV3 are opened, and the valves LV1˜LV3 are closed so that gas is evacuated from the processing space 11A.
Then, in step 6, the evacuation valve EV and the vent valve VV2 are closed and the valve LV2 is opened so that H2O gas is introduced into the processing space 11A from line L2. The H2O gas introduced to the processing space 11A causes oxidation of the metal Hf layer formed on the surface of the substrate W so that a HfO2 film is formed.
After step 6, the process may go back to step 1 to open the evacuation valve EV and the vent valves VV1˜VV3, and close the valves LV1˜LV3 so that gas is evacuated from the processing space 11A.
As is shown in
According to the present embodiment, after the TDMAH precursor introduction step 2, the evacuation step 3 is conducted, which is followed by the hydrogen gas introduction step 4. In this way, residual TDMAH precursor elements may be substantially removed from the processing space 11A before the hydrogen gas is introduced so that a volatile reaction between the hydrogen gas and the residual TDMAH precursor may be prevented and particle generation resulting from such a reaction may thereby be prevented. It is noted that the evacuation step 3 between the TDMAH precursor introduction step 2 and the hydrogen introduction step 4 may be conducted for period of around 1 second. It is also noted that in the evacuation step 3, a purge gas such as nitrogen gas or Ar gas may be introduced to the processing space 11A so that the discharging efficiency may be improved in discharging the residual TDMAH precursor.
According to the present embodiment, in the precipitation (hydrogen introduction) step 4 after the evacuation step 3, since the TDMAH precursor molecules adsorbed to the surface of the substrate W react with the introduced hydrogen gas to desorb the organic functional groups, the HfO2 film formed in step 6 may be free from residual carbon. In this way, a high-quality HfO2 film with little defects may be obtained using an organic metal compound precursor.
It is noted that according to an experiment conducted by the inventor of the present invention, the carbon concentration within a HfO2 film formed according to the present embodiment is reduced to 1×1019 cm−3 or lower. Also, it is noted that the HfO2 film formed in the above-described manner does not include halogen such as chloride since a chloride compound is not used as the precursor.
According to the above-described example, in the chemical adsorption step 2, a TDMAH layer having a one-molecule layer thickness is formed on the surface of the substrate W by controlling the TDMAH gas adsorption time or substrate temperature, and in the oxidation step 6, oxidation of the one-molecule thickness TDMAH film is realized to form a one-molecule thickness HfO2 film. In this case, the processes illustrated in
It is noted that in the above-described example, TDMAH is used as the amine-based organic metal compound precursor of the metal Hf. However, the present invention is not limited to such an example, and other materials such as tetrakis(diethylamino)hafnium (Hf[N(CH2CH3)2]4) may be used as an organic metal compound precursor of Hf.
It is also noted that the present invention is not limited to using an amine-based organic metal compound precursor of the metal element Hf, and in alternative embodiments, amine-based organic metal compound precursors of Zr such as tetrakis(dimethylamino)zirconium (Zr[N(CH3)2]4) and tetrakis(diethylamino)zirconium (Hf[N(CH2CH3)2]4) may be used to form a ZrO2 film, for example.
Further, the present invention is not limited to forming a HfO2 film or a ZrO2 film, and in alternative embodiments, a silicate film such as a HfSiO4 film or a ZrSiO4 film, or an aluminate film such as a HfAl2O4 film or a ZrAl2O4 film may be formed, for example. It is particularly noted that trimethylaluminum (Al(CH3)3) may be used as an organic metal compound precursor of Al, and tetrachlorosilane (SiCl4) may be used as a precursor of Si.
In the case of forming a silicate film or an aliminate film, it is noted that a compound film with desirable characteristics may be formed by forming a HfO2 molecular layer in stage I of the process sequence of
It is noted that in fabricating a p-channel MOS transistor, after forming a polysilicon gate electrode, boron (B) contained in the gate electrode is diffused into the channel region during a thermal process that is subsequently performed, and as a result fluctuation occurs in the threshold voltage. In response to such a problem, typically, nitrogen (N) is introduced to a gate oxide film in order to prevent the diffusion of boron (B). According to the present embodiment in which an amine-based precursor is used, nitrogen may be readily introduced into the gate oxide film. For example, in the hydrogen gas introduction step (step 4 of
In the process sequence of
According to the present example, in step 4, hydrogen molecules are adsorbed onto a HfO2 film that is formed in the previous steps, and excessive hydrogen molecules are discharged from the processing space 11A in the evacuation step 1 of the next stage II.
Then, in step 2 of stage II, when an amine-based organic metal compound precursor of Hf such as TDMAH is introduced to the processing space 11A, the reaction (1) as is described above occurs when the TDMAH molecules are adsorbed onto the HfO2 film formed in the previous steps so that organic functional groups is desorbed and the metal Hf is precipitated.
Then, after removing excessive TDMAH precursor molecules from the processing space 1A in step 3, oxidation is conducted on the metal Hf layer formed by the metal Hf adsorbed in step 6 so that a high-quality HfO2 film with a low carbon concentration is formed.
It is noted that, as with the previously described embodiment, the present embodiment is not limited to using TDMAH as the amine-based organic metal compound precursor, and the film to be formed in the present embodiment is not limited to a HfO2 film.
In the process sequence of
Then, after conducting the TDMAH introduction step 2, the evacuation step 5 is conducted followed by the hydrogen gas introduction step 4.
As can be appreciated from the above descriptions, in the process sequence according to the present embodiment, the hydrogen gas introduction step is conducted before and after the amine-based organic metal compound precursor introduction step 2 to ensure the desorption of organic functional groups from the organic metal compound precursor molecules adsorbed on the substrate being processed. In this way, the amount of carbon remaining in the resulting high-K dielectric film (e.g., HfO2 film) may be reduced.
The MOCVD apparatus 10A of
Referring to
Then, in step 14, H2O gas and hydrogen gas are introduced into the processing space 11A along with nitrogen carrier gas via line L2. As a result, oxidation is realized on the TDMAH molecular layer covering the surface of the substrate being processed in the processing space 11A, and at the same time, organic functional groups are desorbed.
It is noted that by repeatedly conducting the sequence of process steps 11˜14 as stages I, II, III, IV, . . . and so forth, a high-K dielectric film such as a HfO2 film with a low carbon concentration may be efficiently formed on a substrate.
FIGS. 8A˜8D are diagrams showing process steps for fabricating a super-high-speed MOS transistor according to a fifth embodiment of the present invention.
According to the present embodiment, in the process step shown in
By conducting any one of the process sequences described in relation to
Also, in the process step illustrated in
Then, in the process step of
Then, in the process step of
Then, in the process step of
The MOS transistor formed in the manner described above uses a high-K dielectric film such as a HfO2 film as the gate dielectric film 22G. Thereby, even in a case where the gate length is reduced to 0.1 μm or less, the gate dielectric film may still have a sufficient physical film thickness so that an increase of gate leak currents may be prevented. Also, it is noted that since the carbon concentration in the gate dielectric film 22G is reduced according to the present embodiment, a highly reliable film that is free of defects such as voids may be formed.
FIGS. 9A˜9C are diagrams showing process steps for fabricating a MOS capacitor according to a sixth embodiment of the present invention.
According to the present embodiment, in the process step as is shown in
Then, a polysilicon lower electrode 43 that is doped by a p-type or n-type impurity according to the conductivity type of the diffusion region 41A is formed on the insulating film 42. The polysilicon lower electrode 43 is arranged to come into contact with the diffusion region 41A via the contact hole formed on the insulating film 42.
Then, in the process step of
Then, in the process step of
According to the present embodiment, in the high-K dielectric film such as a HfO2 film that is used as the capacitor dielectric film 44, the concentration of an impurity such as carbon derived from the organic metal compound precursor is reduced so that a highly reliable film capable of effectively preventing the generation of leak currents is realized. It is noted that by incorporating the carbon removal step, the generation of voids in the dielectric film as a result of oxidation of carbon within the dielectric film may be effectively prevented. In this way, electric field concentration occurring at the voids may be prevented.
Also, it is noted that in the present embodiment, the capacitor dielectric film 44 is formed through adsorption of an organic metal compound precursor gas and oxidation of a resulting metal film. Accordingly, the capacitor dielectric film 44 may be evenly formed at a uniform film thickness even when the lower electrode 43 has a complicated structure.
The capacitor formed in the above-described manner may be used to construct a DRAM, for example.
The MOCVD apparatus 60 of
The processing chamber 61 also has an evacuation port 61B from which gas is evacuated via an evacuation valve EV. Also, a heater 62 is provided at the outer side of the processing chamber 61.
The batch processing MOCVD apparatus 60 as is described above includes lines L1, L2, and L3 for supplying an amine-based organic metal compound precursor such as TDMAH, an oxidizing agent such as H2O, and hydrogen gas, respectively. By alternatingly supplying the respective gases according to any one of the process sequences described in relation to FIGS. 2˜7, volatile reaction may be prevented from occurring within the processing chamber 61 and organic functional groups may be effectively removed from the organic metal compound precursor so that the carbon concentration within the resulting high-K dielectric film may be effectively reduced.
According to an embodiment of the present invention, amine-based organic metal compound precursor molecules are adsorbed onto the surface of a substrate being processed after which the residual amine-based organic metal compound precursor molecules are evacuated from the surface of the substrate, and then the adsorbed amine-based organic metal compound precursor molecules are reacted with hydrogen gas so that a film made of a metal element included in the organic metal compound precursor is formed to cover the surface of the substrate. By forming the metal film in the manner described above, carbon may be effectively removed from the film so that the resulting metal film may be substantially free of carbon. Then, an oxidation process is conducted on this metal film to form a desired dielectric film. According to the present embodiment, the amine-based organic metal compound precursor gas that may cause volatile reaction with hydrogen gas is removed from the processing space of the substrate before the hydrogen gas reaction process is conducted so that particle generation may be prevented, for example.
Further, it is noted that the present invention is not limited to the specific embodiments described above, and variations and modifications may be made without departing from the scope of the present invention.
This application is a U.S. continuation application filed under 35 USC 111 (a) claiming benefit under 35 USC 120 and 365 (c) of PCT application JP2003/004919, filed on Apr. 17, 2003, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP03/04919 | Apr 2003 | US |
| Child | 11098395 | Apr 2005 | US |
