Patent Application
20110312179
The present invention relates to a substrate processing method and a substrate processing apparatus which form an insulating film, more specially it relates to a substrate processing method and a substrate processing apparatus of a semiconductor device having a high-k dielectric film.
There has been a problem of increase of a gate-leak current due to reduction in film thickness of a gate insulating film in developing a leading-edge CMOS (complementary MOS) device in which miniaturization of transistors is advancing. Moreover, in developing an MONOS (Metal Oxide Nitride Oxide Semiconductor) device in which miniaturization of non-volatile semiconductor elements is advancing, there has been a problem of maintaining a retention characteristic in spite of reduction of an operational voltage due to reduction in film thickness of a blocking layer for preventing leakage of charges accumulated in a charge accumulation layer to the side of a gate electrode.
Hence, a technology for reducing a gate-leak current and thinning the EOT (Equivalent Oxide Thickness) of a silicon oxide film by thickening a physical film layer using a high-k material as the gate insulating film of a CMOS device or the blocking layer of an MONOS device, has been investigated. As typical high-k materials, oxides containing Ta, Al, Zr, Hf, La, etc. are included.
As for means for forming films of the above-mentioned high-k materials, methods for forming a metal oxide film by a CVD (Chemical Vapor Deposition) process, an Atomic Layer Adsorption/Deposition method, and a sputtering method, are included.
In Patent Document 1, as a technology for an Atomic Layer Adsorption process of HfO2, a technology using Hf [N(C2H5)2]4 (tetrakis (dimethylamino) hafnium) as a metal raw material gas and O3 as an oxidizer is disclosed, where HfO2 is formed by alternately repeating an Hf [N(C2H5)2]4 supply step, a purge step, an O3 supply step, and a purge step in this order on a substrate.
Moreover, in Non-Patent Document 1, an Atomic Layer Adsorption process of La2O3 using La(i-PrCp)3 (tris(isopropyl-cyclopentadienyl)lanthanum) as a metal raw material gas and using O3 as an oxidizer is described.
Next, in Patent Document 2, a method for forming an oxide thin film by means of a sputtering method is disclosed, which includes a process where a first step of reactive sputtering deposition accompanied with a chemical reaction with a gas containing the element of a thin film raw material or the discharged plasma of the gas and a second step of decomposing and exciting a reactive gas at the deposition surface or near the surface using plasma that substantially does not cause sputtering to occur under an electric field capable of decomposing a gas used for oxidation in a gas atmosphere containing a gas in which deposition does not occur or occurs at a rate much smaller than that of the first step are carried out alternately for a plurality of times.
Furthermore, in Patent Document 3, a method for forming Al2O3 by means of a sputtering method is disclosed, where Al2O3 is formed by alternately repeating a step of forming an Al metal film and a step of oxidizing the Al film with plasma generated by an RF coil while introducing O2 gas.
Furthermore, in Patent Document 4, a method for forming MOSFET by depositing a metal gate by vapor deposition on a high-k dielectric is disclosed, which includes: a annealing step of annealing a substrate on which a high-k dielectric film is deposited by vapor deposition in a thermal annealing module; and a vapor deposition step of depositing a metal gate material by vapor deposition on the annealed substrate in a metal gate vapor deposition module, wherein the annealing step and the vapor deposition step are continuously carried out without breaking a vacuum.
Furthermore, in Patent Document 5, a method for forming a hafnium silicate high-k dielectric film is disclosed, where on a silicon substrate in which a silicon oxynitride film is formed a hafnium layer is deposited by means of a sputtering method, then the substrate is continuously subjected to thermal processing in a film formation chamber, subsequently the processed substrate is taken out from inside the film formation chamber, and subjected to thermal processing in a nitrogen atmosphere so as to compensate the oxygen deficiencies in the film.
However, the above-mentioned film formation technologies have the following problems, respectively.
First, Atomic layer Adsorption/Deposition methods as disclosed in Patent Document 1 and Non-Patent Document 1 has a problem in that since a raw material gas containing C is used as a metal raw material gas, C remains in a metal film, leading to increase of electric properties such as a leak current.
Second, as indicated in Non-Patent Document 1, it is demonstrated that the thickness of La2O3 film for 0 to 15 cycles tends to saturate with respect to the number of cycles. Thus, Atomic layer Adsorption/Deposition method has a problem of difficulty in controlling the thickness of a metal oxide film in an ultra thin film region.
Third, the methods disclosed in Patent Document 2 and Patent Document 3 have an advantage in that the area of oxygen deficiencies in the metal oxide film deposited on a substrate is compensated by oxygen atoms. However, since oxygen plasma is used for oxidation, traps of hot carriers tend to be formed in the metal film due to plasma damage, resulting in problems of fluctuation of the threshold voltage for a CMOS device and degradation of the retention characteristic due to leakage via the traps for an MONOS device.
Fourth, since in the method disclosed in Patent Document 4, a film formation step and an annealing step are carried out in a different vessel, respectively, there occur problems of decrease in throughput and difficulty in forming a high-k insulating film with a stoichiometric composition. Particularly, in case of forming a thick insulating film, there occurs a problem of carrying out the film formation step and the annealing step many times repeatedly.
Fifth, in the method disclosed in Patent Document 5, a film formation step and an annealing step are carried out in one and the same vessel. However, in the method disclosed in Patent Document 5, a thermal treatment step is performed in a state containing a lot of oxygen deficiencies to diffuse the metal film-formed in a silicon oxide under film, thereby forming a metal silicate layer. Thus, although the method is suitable for formation of a silicate layer utilizing an interface reaction, it is not suitable for formation of the blocking film of a trap memory, because a trap layer due to the oxygen deficiencies and the interface reaction may be formed. Moreover, in Patent Document 5, it is also described that even when the oxidation step is carried out in another chamber and continuous thermal treatment is performed in a film formation chamber, it is necessary to perform thermal treatment again in a nitrogen atmosphere, because oxygen deficiencies occur in the film. Moreover, although the method disclosed in Patent Document 5 is suitable for formation of a dielectric film having a thickness of about 1 nm, there occurs a problem in that the number of steps increases when the blocking film for an MONOS device requiring to have a thickness of, for example, 5 nm or more is formed, because the film formation step and the thermal treatment step (annealing step) have to be repeated for several times. That is, in order to achieve the requirement according to the method disclosed in Patent Document 5, the steps of forming a metal film having a thickness of about 3 nm in a vessel, oxidizing the metal film in another vessel, forming a metal film having a thickness of about 3 nm on the oxidized metal film again, and oxidizing the metal film in the other vessel, . . . have to be repeated for several times. Thus, there occurs a problem in that the number of steps increases.
The present invention is devised to solve the above-mentioned problems, and the object thereof is to provide a substrate processing method and a substrate processing apparatus which are capable of forming a high-k dielectric film having few oxygen deficiencies and traps due to hot carriers in one and the same vacuum vessel by means of a sputtering method.
In order to achieve the above-mentioned object, the present invention has the following configuration.
One aspect of the present invention is a substrate processing method, comprising a first step of heating a to-be-processed substrate arranged in a vacuum vessel and depositing a metal film on the substrate by physical vapor deposition using a target; and a second step of supplying a gas containing an element for oxidizing a metal film in the vacuum vessel to oxidize the metal film by a thermal oxidation reaction.
Moreover another aspect of the present invention is a substrate processing apparatus, comprising: a film forming treatment chamber; a substrate holding table for holding a to-be-processed substrate in the film forming treatment chamber; a heating device for adjusting the temperature of the substrate holding table; an oxidation gas introduction means for introducing an oxidation gas in the film forming treatment chamber; an inert gas introduction means for introducing an inert gas in the film forming treatment chamber; a high-frequency supply means for supplying a high-frequency electric power to a target containing an element constituting a metal film; and a control mechanism, wherein when a metal film is formed on the to-be-processed substrate in the film forming treatment chamber, the control mechanism controls the heating device so as to heat the to-be-processed substrate and controls the inert gas introduction means and the high-frequency supply means so as to deposit a metal film on the to-be-processed substrate being heated, and wherein when the deposited metal film is oxidized in the film forming treatment chamber, the control mechanism controls the oxidation gas introduction means so as to supply the oxidation gas on the deposited metal film and controls the heating device so as to oxidize the metal film by a thermal oxidation reaction.
Moreover, another aspect of the present invention is a method for manufacturing a MOS-FET including a high-k dielectric film, the method comprising: a first step of heating a to-be-processed substrate arranged in a vacuum vessel and depositing a metal film on the substrate by physical vapor deposition using a target; and a second step of supplying a gas containing an element for oxidizing a metal film in the vacuum vessel to oxidize the metal film by a thermal oxidation reaction.
Moreover, another aspect of the present invention is a method for manufacturing a non-volatile memory element including a high-k dielectric film, the method comprising: a first step of heating a to-be-processed substrate arranged in a vacuum vessel and depositing a metal film on the substrate by physical vapor deposition using a target; and a second step of supplying a gas containing an element for oxidizing a metal film in the vacuum vessel to oxidize the metal film by a thermal oxidation reaction.
Further, another aspect of the present invention is a computer readable recording medium having a program recorded therein for causing a computer to execute a method for forming a MOS-FET including a high-k dielectric film, the method comprising: a first step of heating a to-be-processed substrate arranged in a vacuum vessel and depositing a metal film on the to-be-processed substrate by physical vapor deposition using a target; and a second step of supplying a gas containing an element for oxidizing a metal film in the vacuum vessel to oxidize the metal film by a thermal oxidation reaction.
According to the present invention, a method for forming a metal oxide film on a to-be-processed substrate by physical vapor deposition using a sputtering target, while heating the substrate arranged in a vacuum vessel, performs a first step of depositing the metal film on the substrate and a second step of, without including a deposition step of a metal film, supplying a gas containing an element oxidizing the metal film to oxidize the metal film by only a thermal decomposition reaction. This enables a metal oxide film having few oxygen deficiencies to be formed in one and the same vacuum vessel, in which the leak current due to remained C does not increase and formation of traps in the metal oxide film derived from plasma damage is suppressed.
Hereinafter, with reference to drawings, embodiments of the present invention will be described, however, the present invention should not be limited to the embodiments.
The present invention is based on a new finding that, by carrying out in one and the same vacuum vessel, while heating the substrate, a first step of depositing a metal film on a to-be-processed substrate and a second step of, without including a deposition step of a metal film, supplying a gas containing an element oxidizing the metal film in the vessel to oxidize the metal film by a thermal decomposition reaction, oxygen deficiencies in the metal oxide can be compensated without accompanying formation of trap sites due to plasma damage in the metal oxide film.
The reason why the inventor of the present invention has reached the new finding is as follows. That is, when the deposition step and the oxidation step of a metal film are carried out in different vessels, respectively, since there is a concern that only the surface area of the metal film may be oxidized, completely oxidizing a metal film with a thickness of, e.g., 20 nm into a perfect insulating film using the different vessels seems to be difficult. Moreover, there occurs a problem in that diffusion of metal elements remained in the film due to oxygen deficiencies in the film into the under substrate accelerates an interface reaction to form an interface layer. On the other hand, according to the present invention, since the deposition step and the oxidation step of a metal film are carried out in one and the same vessel, it is not necessary to have a concern that only the surface area of the metal film may be oxidized. Moreover, since the oxygen deficiencies in the film are suppressed, formation of the interface layer by the reaction between the metal elements and the under substrate can be prevented or suppressed.
A first feature of the present invention is based on the new finding, specifically in carrying out in one and the same vacuum vessel, while heating the substrate, a first step of depositing a metal film on a to-be-processed substrate arranged in a vacuum vessel by physical deposition using a target and a second step of supplying a gas containing an element oxidizing the metal film to oxidize the metal film by a thermal oxidation reaction.
Next, the configuration and the operation of a substrate processing apparatus together with a substrate processing method according to the present invention will be described.
The outline view of a processing apparatus according to the present invention is illustrated in
Next, in a second step, a gas involving in oxidation of a metal film is introduced into the film forming treatment chamber 100 from an oxidation gas source 115 via a valve 116, a mass-flow controller 117, and a valve 118. The inert gas in the first step and the oxidation gas in the second step are exhausted by an exhaustion pump 121 via a conductance valve 120. Pressures in the film forming treatment chamber in the first and the second steps are controlled to predetermined values, by the conductance valve 120.
The valves 112, 114, 116 and 118 can carry out open/close control by a control device 300 via controlling input/output ports 200, 201, 202 and 203, respectively. Moreover, as for the mass-flow controllers 113 and 117, the flow rates can be controlled by the control device 300 via controlling input/output ports 204 and 205, respectively. Moreover, as for the conductance valve 120, the degree of opening can be adjusted by the control device 300 via a controlling input/output port 206. Moreover, as for the heater 105, the temperature can be adjusted by the control device 300 via a controlling input/output port 207. Moreover, as for the rotational state of the substrate holding table 103, the rotation number can be adjusted by the control device 300 via an input/output port 208. Moreover, as for the high-frequency power source 109, the frequency and the supply power can be adjusted by the control device 300 via an input/output port 209. Moreover, as for the matching box 108, the matching of supplied power can be adjusted by the control device 300 via an input/output port 210.
First, a first step of forming a metal film according to the present invention will be described. The control device 300 introduces an inert gas from the inert gas source 111 into the film forming treatment chamber 100 by opening the valves 112 and 114 and adjusting the flow rate while controlling the mass-flow controller 113. It is preferable for the inert gas to contain at least one gas selected from Ar, Kr and Xe. At that time, the control device 300 adjusts the partial pressure of the inert gas in the film forming treatment chamber 100 to a predetermined pressure by the conductance valve 120.
Next, the control device 300 supplies desired electric power to the target 106 by controlling the high frequency power source 109 and the matching box 108. Next, the control device 300 opens a shielding plate 119 shielding the target 106 and the to-be-processed substrate 102, to form a metal film on the substrate 102. At that time, the control device 300 can set the temperature of the to-be-processed substrate 102 to a predetermined temperature by controlling the heater 105. The predetermined temperature can be set suitably depending on an oxidation gas to be introduced, for example, when H2O is used as the oxidization gas, a desired metal oxide film can be formed at a substrate temperature of 300° C. Moreover, when O2, O3, N2O and D2O are used as the oxidization gas, a desired metal oxide film can be formed at a substrate temperature of 600° C.
While heating the to-be-processed substrate 102 in this manner, a metal film is formed on the to-be-processed substrate 102 by physical vapor deposition using a target. The control device 300 can control the formation rate and the thickness of the film to be formed by the power and time supplied to the target 106 and the time during which the shielding plate 119 is opened. After a predetermined metal film is formed, the control device 300 stops to supply power by closing the shielding plate 119 and by controlling the high-frequency power source 109 and the matching box 108, to stop forming a metal film on the to-be-processed substrate 102. Furthermore, the control device 300 stops to introduce the inert gas in the film forming treatment chamber 100 by closing the valves 112 and 114 and by controlling the mass-flow controller 113 to stop adjusting the flow rate, causing the first step of forming a metal film to be completed.
In addition, the metal film to be formed on the to-be-processed substrate 102 preferably contains at least one element selected from the group consisting of Hf, Zr, Al, La, Pr, Y, Ti, and, Ta.
Next, a second step of forming a metal oxide film according to the present invention will be described. In the film forming treatment chamber 100 in which the first step is carried out, the control device 300 opens the valves 116 and 118, controls the mass-flow controller 117 to adjust the flow rate, and introduces an oxidation gas (oxidizing agent) from the oxidation gas source 115 into the film forming treatment chamber 100. The oxidation gas preferably contains at least an atom or a molecule selected from the group consisting of an oxygen radical atom, an oxygen radical molecule, O2, O3, N2O, H2O, and D2O (heavy water). At that time, the control device 300 can adjust the partial pressure of the inert gas in the film forming treatment chamber 100 to a desired pressure by the conductance valve 120. Formation of the metal oxide film can be controlled by the introduction time of the oxidation gas and the temperature of the to-be-processed substrate 102. That is, the control device 300 sets the temperature of the to-be-processed substrate 102 to a predetermined temperature by controlling the heater 105. It is preferable for the temperature of the to-be-processed substrate 102 to be equal to or higher than 200° C. in order to accelerate the thermal oxidation reaction, and it is preferable for the temperature to be equal to or lower than 600° C. in order to suppress oxidation of the under substrate.
Next, the control device 300 completes the second step of forming a metal oxide film by closing the valves 116 and 118 and by controlling the mass-flow controller 117 to stop adjusting the flow rate. As described above, since the formation of a metal oxide film according to the present invention is carried out by only the thermal oxidation reaction of the metal film due to the oxidation gas, oxygen deficiencies can be compensated without forming traps derived from plasma damage in the metal oxide film.
Moreover, as described in
Moreover, although the first step and the second step are carried out once, respectively, in
The feature of the control device according to the present embodiment is in that the device is controlled so as to carry out the first step and the second step described in
Specifically, as described in
Next, by controlling the high-frequency power source 109 and the matching box 108, the control device 300 applies desired electric power to the target 106, and by opening the shielding plate 119, forms a metal film on the substrate 102 by means of sputtering. Next, the device 300 closes the shielding plate 119, and by controlling the high-frequency power source 109 and the matching box 108, stops to supply electric power to the target 106. Next, the device 300, by closing the valves 112, 114, 116 and 118, and by controlling the mass-flow controllers 113 and 117, stops to adjust the flow-rate. By these steps, the sputtering process mentioned above will be completed.
Step-1: By vapor deposition, depositing a preliminary film for a high-k dielectric.
Step-2: Performing thermal annealing process under an oxygen atmosphere to form the high-k dielectric.
Step-3: Cooling a wafer.
Step-4: By vapor deposition, depositing a metal electrode material.
A starting wafer may be structured so as to have or not to have a thin SiO2 or SiON layer 102a deposited initially on a to-be-processed substrate 102. In
Similarly, in this case, the starting material 102b can have a lamination structure of the two or more films mentioned above. Such a lamination structure of two or more films includes, for example, Hf/SiN/Hf and HfN/AlN/Hf.
Usually, Hf, Zr, Ti or Ta is used as the metal target 106. However, another metal target can also be used. When a metal-semiconductor alloy is deposited, the semiconductor material is preferably Si.
Although not so important, the film thickness of the starting material 102b mentioned above is usually maintained to be equal to or smaller than 5 nm, in general, it is maintained to be about 2 nm.
As mentioned above, after the starting film 102b is deposited by vapor deposition, the to be processed substrate 102 is generally heated to a high temperature over 400° C. under an oxygen gas atmosphere, and this oxidizes the starting film 102b, which is a starting material, (
After the heat annealing process is completed, the to-be-processed substrate 102 is transferred to a cooling module (not illustrated in the figure), where it is cooled to a desired temperature, preferably to a room temperature.
The substrate 102 is transferred to a PVD module (not illustrated in the figure), where a gate electrode 26 is deposited by vapor deposition thereon (
A MOS field effect transistor (FET) 90 of
With reference to drawings, the first embodiment of the present invention will be described in detail.
Here, a film was formed under the following conditions, the substrate temperature: 300° C.; the Hf target power: 600 W; the pressure of the sputtering gas: 0.03 Pa; the flow rate of Ar: 25 sccm; and the flow rate of oxygen gas: 50 sccm.
By using the above-mentioned formation step, HfO2 with a thickness of 20 nm was formed. Next, a TiN film 304 with a thickness of 10 nm was deposited on HfO2 by means of a sputtering method. A Ti metal target was used as a target, and argon and nitrogen was used as a sputtering gas. Next, a MIS capacitor was formed by working the TiN film to a desired size using a lithography technology and an RIE technology.
As a result of evaluating the CV (Capacitance-Voltage) characteristic of HfO2 produced as mentioned above, the hysteresis shift resulting from the oxygen deficiencies in the film was not observed. Moreover, when the cross-section of the interface between the silicon dioxide film of the under layer and HfO2 was observed by a TEM, the interface reaction layer due to diffusion of Hf was not observed at the interface. Thus, according the first embodiment of the present invention, the method for forming a metal oxide film on a to-be-processed substrate by physical vapor deposition using a sputtering target, while heating the to-be-processed substrate arranged in a vacuum vessel, performs a first step of depositing a metal film and a second step of, without including a deposition step of the metal film, supplying a gas containing an element that oxidizes the metal film to oxidize the metal film by only a thermal decomposition reaction. It was confirmed that, by these steps, a film was obtained in one and the same vacuum vessel, in which the leak current due to remained C did not increase, the formation of traps in the metal oxide film derived from plasma damage was suppressed, and few oxygen deficiencies were present.
Moreover, in the present embodiment, it was confirmed that the same effects was also obtained even when Al2O3, ZrO2, Ta2O3, TiO2, La2O3 and Y2O3 were formed using Al, Zr, Ta, Ti, La and Y as a metal film.
Moreover, although oxygen was used as the oxidation gas in the present embodiment, even when one oxidation gas selected from the group consisting of an oxygen radical atom, O3, N2O, H2O and D2O was used, the same effects was obtained.
With reference to drawings, the second embodiment of the present invention will be described in detail.
a) to 11(c) illustrate each step of a method for manufacturing a semiconductor device according to the second embodiment of the present invention, respectively.
First, as illustrated in
Next, poly-Si 405 with a thickness of 150 nm was formed on a dielectric film 404, and then the laminated body illustrated in
Further, as illustrated in
As a result of evaluating the electrical properties of the produced semiconductor device, a hysteresis shift resulting from oxygen deficiencies in the film was not observed. Moreover, when the cross-section was observed by a TEM, the interface reaction layer formed by diffusion of Hf in the interface between the silicon oxide under film and HfO2 was not observed.
Moreover, in the present embodiment, it was confirmed that the same effects was also obtained even when Al2O3, ZrO2, Ta2O3, TiO2, La2O3 and Y2O3 were formed using Al, Zr, Ta, Ti, La and Y as a metal film.
Moreover, although oxygen was used as the oxidation gas in the present embodiment, even when one oxidation gas selected from the group consisting of an oxygen radical atom, O3, N2O, H2O and D2O was used, the same effects were obtained.
a) to 12(c) are cross-section views illustrating each step of a method for manufacturing a semiconductor device according to the third embodiment of the present invention, respectively.
First, as illustrated in
Next, a poly-Si film with a thickness of 150 nm was formed thereon as a gate electrode 506, and then, the laminated body illustrated in
Further, as illustrated in
As a result of evaluating the electrical properties of the produced semiconductor device, degradation of the retention characteristic resulting from oxygen deficiencies in the aluminum oxide film was not observed.
As mentioned above, according to the present embodiment, using the substrate processing method and the substrate processing apparatus according to the present invention for forming the blocking insulating film of an MONOS nonvolatile memory element, a semiconductor device capable of improving the retention characteristic was able to be obtained.
Moreover, in the present embodiment, it was confirmed that the same effects were obtained even when Al2O3, ZrO2, Ta2O3, TiO2, La2O3 and Y2O3 were formed using Al, Zr, Ta, Ti, La, and Y as a metal film.
Moreover, although oxygen was used as the oxidation gas in the present embodiment, even when one oxidation gas selected from the group consisting of an oxygen radical atom, O3, N2O, H2O and D2O was used, the same effects were obtained.
In addition, the control mechanism 300 may be provided separately from the substrate processing apparatus 301, and may be built in the substrate processing apparatus 301.
A processing method in which a program for operating the configurations of the embodiments mentioned above is stored in a storage medium so as to achieve the functions of the embodiments, and the program stored on the storage medium is read out as a code and is executed by a computer, is also included in the scope of the embodiments. That is, a computer-readable storage medium is also included in the scope of the embodiments. Moreover, not only the storage medium on which the computer program is stored, but also the computer program itself is included in the scope of the embodiments.
A floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a non-volatile memory card and a ROM can be used as such a storage medium.
Moreover, not only a single program stored on the storage medium for executing processing, but also a program running on an OS for executing the operations of the embodiments together with the functions of other software and another extension board, is included in the scope of the embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008331693 | Dec 2008 | JP | national |
This application is a continuation application of International Application No. PCT/JP2009/071321, filed Dec. 22, 2009, which claims the benefit of Japanese Patent Application No. 2008-331693, filed Dec. 26, 2008. The contents of the aforementioned applications are incorporated herein by reference in their entities.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2009/071321 | Dec 2009 | US |
| Child | 13115410 | US |
