JP5463423B2 - Charge trap type memory device and method of manufacturing the same - Google Patents

Description

  The present invention relates to a nonvolatile semiconductor memory device using an electrode film and a manufacturing method thereof, and more particularly to a charge trap memory device and a manufacturing method thereof.

  Development of non-volatile semiconductors that can be made denser and finer than existing floating gate types is underway. For example, in a MONOS (Metal Oxide Nitride Oxide Semiconductor) type charge trap memory device, a nitride film and an oxide film are stacked on an oxide film, and a gate electrode is provided on the oxide film, and sandwiched between the oxide films. Charges are accumulated in the nitride film and the memory is retained.

  The configuration of a conventional charge trap memory device will be described with reference to FIG. 14 (see Patent Document 1). The conventional charge trap memory device 800 has a stacked structure in which a tunnel oxide film 811, a charge trap film 812, a blocking insulating film 813, and a gate electrode 814 are formed in this order from below on a silicon substrate 810.

The tunnel oxide film 811 includes a silicon oxide film (SiO ₂ film), and the charge trap film 812 includes a silicon nitride film (SiN film) or a silicon oxynitride film (SiON). , Silicon oxide film (SiO ₂ film) or Al ₂ O ₃ film, high dielectric constant film (High-k film), for example, HfO ₂ , ZrO ₂ , Ta ₂ O ₅ , Y ₂ O _3, etc. The gate electrode 814 includes a polysilicon film, a TaN film, a metal film (W, Pt, etc.), a TiN film, and the like.

  In the charge trap memory device 800 having the above-described configuration, a negative voltage (from the silicon substrate 810 side to the charge trap film 812 is applied to the charge trap film 812 by applying a predetermined voltage, for example, a +18 V pulse voltage from the write / erase control circuit 820. Electrons) are trapped and a write operation is performed. Further, a negative voltage (electrons) trapped in the charge trap film 812 is detrapped by applying a pulse voltage of −18 V (or −20 V), for example, from the write / erase control circuit 820 to the gate electrode 814. Then, erase operation is performed.

The configuration of another conventional charge trap memory device will be described with reference to FIG. 15 (see Patent Document 2). A semiconductor memory device 901 in FIG. 15 includes a substrate 911, a first gate insulating film 921, a charge storage insulating film 922, a second gate insulating film 923, a gate electrode 924, a sidewall insulating film 931, and an interlayer An insulating film 941. The substrate 911 includes a silicon substrate or an SOI (Semiconductor On Insulator) substrate. A source diffusion layer 951 and a drain diffusion layer 952 are provided on the substrate 911. The first gate insulating film 921 is also called a tunnel insulating film, and includes a silicon oxide film or an ONO-type stacked film including a first silicon oxide film, a silicon nitride film, and a second silicon oxide film. The second gate insulating film 923 is also called a blocking insulating film, and includes a high-k insulating film such as an Al ₂ O ₃ layer, an HfAlOX layer, or an HfO ₂ layer. The gate electrode 924 is also called a control gate, and includes a stacked film including a NiSi layer or a CoSi ₂ layer, a TaN layer, a WN layer, and a W layer. Sidewall insulating film 931 includes a nitride film such as a silicon nitride film. The interlayer insulating film 941 includes a silicon oxide film. In FIG. 15, S1 is a side surface in the bit line direction of the charge storage insulating film 922, S2 is a side surface in the bit line direction of the second gate insulating film 923, S3 is a side surface in the bit line direction of the gate electrode 924, and W1 is The width of the charge storage insulating film 922 in the bit line direction, W2 is the width of the second gate insulating film 923 in the bit line direction, and W3 is the width of the gate electrode 924 in the bit line direction.

JP 2010-192592 A JP 2010-27707 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a charge trap memory device and a manufacturing method thereof in which leakage current during erasure is reduced and reliability is improved. It is.

In order to achieve such an object, the first aspect of the present invention has a laminated structure in which a tunnel oxide film, a charge trap film, a blocking insulating film, and a gate electrode are formed in this order on a silicon substrate. A method for manufacturing a charge trap type memory device that performs writing and erasing of information by trapping and detrapping charges from the silicon substrate side to the charge trap film by applying a voltage to the gate electrode, Preparing the silicon substrate on which the tunnel oxide film, the charge trap film, and the blocking insulating film are sequentially formed; and forming a metal oxynitride layer containing W, N, and O on the blocking insulating film And forming a metal nitride layer containing W and N on the metal oxynitride layer, the metal oxynitride And forming the metal layer and the metal nitride layer in a vacuum vessel in a mixed atmosphere of a reactive gas and an inert gas, the metal comprising the metal contained in the metal oxynitride layer and the metal nitride layer. It is a step of magnetron sputtering a target, the reactive gas in the step of forming the metal oxynitride layer is oxygen and nitrogen, and the reactive gas in the step of forming the metal nitride layer is nitrogen It is characterized by.

  According to the present invention, in a charge trap memory device, a leakage current at the time of erasure is obtained by using a metal oxynitride layer (for example, a WON film) having a high work function and containing W, N, and O as a gate electrode. And the reliability of the charge trap memory device is improved. Further, in addition to the effect, a metal nitride layer (for example, WN film) containing W and N is laminated on a gate electrode made of a metal oxynitride layer containing W, N, and O to form a metal. Diffusion can be suppressed, and heat resistance is improved.

It is sectional drawing of the MONOS type | mold charge trap type | mold apparatus which formed the electrode film by one Embodiment of this invention. It is the figure which showed the outline of an example of the processing apparatus used for the formation process of the metal oxynitride film | membrane which concerns on one Embodiment of this invention. It is the figure which made the discharge characteristic of the WN film | membrane which concerns on one Embodiment of this invention. It is the figure which made the discharge characteristic of the WON film | membrane which concerns on one Embodiment of this invention. It is the figure which showed the film-forming speed | rate of the WN film | membrane which concerns on one Embodiment of this invention. It is the figure which showed the film-forming speed | rate of the WO film | membrane and WON film | membrane which concerns on one Embodiment of this invention. It is the figure which showed the relationship between the oxygen flow rate at the time of film-forming of the WON film | membrane which concerns on one Embodiment of this invention, and molar ratio O / (O + N + W). It is the figure which showed the molar ratio O / (O + N + W) and specific resistance of the WON film | membrane which concerns on one Embodiment of this invention. It is the figure which showed the molar ratio O / (O + N + W) and density of the WON film | membrane which concern on one Embodiment of this invention. It is the figure which showed the molar ratio O / (O + N + W) and work function of the WON film | membrane which concerns on one Embodiment of this invention. It is the figure which showed the composition of the film thickness direction after laminating | stacking a TiN film | membrane on the WN film | membrane which concerns on one Embodiment of this invention, and baking at 1000 degreeC. It is the figure which showed the composition of the film thickness direction after laminating | stacking a TiN film | membrane on the WON film | membrane which concerns on one Embodiment of this invention, and baking at 1000 degreeC. It is a figure which shows sectional drawing of the MIS capacitor of the 1st Example of this invention. It is a figure which shows the process of the manufacturing method of the semiconductor device of the 2nd Example of this invention. It is a figure which shows sectional drawing of the semiconductor device of the 2nd Example of this invention. It is a figure which shows the structure of the conventional charge trap memory | storage device (patent document 1). It is a figure which shows the structure of the conventional charge trap memory | storage device (patent document 2).

As a result of studying to solve the above problems, the present inventors have formed an electrode film having a high film density and work function by forming a metal oxynitride having a specific composition as a gate electrode of a charge trap memory device. As a result, the present invention was completed.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
One embodiment of the present invention has a stacked structure in which a tunnel oxide film, a charge trap film, a blocking insulating film, and a gate electrode are formed in this order on a silicon substrate having a silicon oxide film on the surface, and the gate electrode By applying a voltage to the charge trap film, the charge trap film is trapped and detrapped to the charge trap film from the silicon substrate side to be directed to a charge trap type storage device for writing and erasing information. In the following, a MONOS (Metal Oxide Semiconductor Oxide Semiconductor) type memory device in which a metal oxynitride film (hereinafter referred to as WON film) containing W, N, and O as constituent elements is formed as a gate electrode film will be described as an example. .

As shown in FIG. 1, after a SiO ₂ layer 2 and a SiN layer 3 are stacked on a silicon substrate 1 having a silicon oxide film with a thickness of 3 nm to 5 nm on the surface, a dielectric film 4 is deposited, and then a WON film An electrode film 5 that functions as a gate electrode is formed. The SiO ₂ layer 2 is a tunnel oxide film, the SiN layer 3 is a charge trap film, and the dielectric film 4 is a blocking insulating film.
The dielectric film 4 as a blocking insulating film is a high dielectric constant insulating film containing metal oxide, metal silicate, or metal oxide or metal silicate into which nitrogen is introduced.

  FIG. 2 shows an outline of an example of a processing apparatus used in the process of forming a gate electrode made of a WON film. The film formation chamber 100 is configured to be heated to a predetermined temperature by the heater 101. The substrate to be processed 102 is heated to a predetermined temperature by the heater 105 via the susceptor 104 incorporated in the substrate support base 103. It is preferable that the substrate support 103 can be rotated at a predetermined rotational speed from the viewpoint of film thickness uniformity.

  In the film formation processing chamber 100, targets 106 and 126 are installed at positions where the target substrate 102 is desired. The targets 106 and 126 are installed on the target holders 108 and 128 via back plates 107 and 127 made of a metal such as Cu. It should be noted that the outer shape of the target assembly in which the targets 106 and 126 and the back plates 107 and 127 are combined may be made of a target material as a single component and attached as a target. That is, a configuration in which the target is installed on the target holder may be used.

  Direct current power sources 110 and 130 for applying sputtering discharge power are connected to the target holders 108 and 128 made of metal such as Cu, and insulated from the wall of the film formation processing chamber 100 at the ground potential by the insulators 109 and 129. Has been.

  Magnets 111 and 131 for realizing magnetron sputtering are disposed behind the targets 106 and 126 as viewed from the sputtering surface. Magnets 111 and 131 are held by magnet holders 112 and 132, and can be rotated by a magnet holder rotating mechanism (not shown). In order to make the erosion of the target uniform, the magnets 111 and 131 rotate during discharge.

  The targets 106 and 126 are installed at offset positions obliquely above the substrate 102. That is, the center point of the sputtering surface of the targets 106 and 126 is at a position displaced by a predetermined dimension with respect to the normal line of the center point of the substrate 102.

  A shielding plate 116 is installed between the targets 106 and 126 and the processing substrate 102 to control film formation on the processing substrate 102 by sputtered particles emitted from the targets 106 and 126 to which power is supplied.

  In one embodiment of the present invention, a dielectric film 4 having a thickness of 10 nm is deposited on the nitride film 3 by sputtering. Next, after the film formation, the dielectric film 4 is obtained by crystallization by annealing.

  Next, a WON electrode 5 as a gate electrode is deposited on the dielectric film 4. As the target, a W metal target 106 may be used. The electrode film 5 is deposited by supplying electric power to the metal target 106 from the DC power source 110 through the target holder 108 and the back plate 107. At this time, an inert gas is introduced into the processing chamber 100 from the vicinity of the target from the inert gas source 201 through the valve 202, the mass flow controller 203, and the valve 204. A reactive gas containing oxygen and nitrogen is supplied from the oxygen gas source 205 and the nitrogen gas source 209 to the vicinity of the substrate in the processing chamber 100 through valves 206 and 210, mass flow controllers 207 and 211, and valves 208 and 212, respectively. To be introduced. The introduced inert gas and reactive gas are exhausted by the exhaust pump 118 via the conductance valve 117.

In an embodiment of the present invention, a substrate temperature of 30 ° C., a target power of W is set to 500 W, Ar is used as an inert gas, Ar is supplied at 25 sccm, and reactive gases such as nitrogen and oxygen are supplied. A film is formed. At this time, the molar ratio O / (O + N + W) of oxygen in the WON film is adjusted by changing the oxygen gas flow rate in the range of 0 sccm to 20 sccm while keeping the nitrogen gas flow rate constant at 15 sccm. In the present specification, the “molar ratio” refers to the ratio of the number of moles, which is the basic unit of the substance amount. The molar ratio can be measured, for example, from X-ray photoelectron spectroscopy, from the binding energy of intrinsic electrons in the substance, the energy level and amount of electrons. Further, sccm = the number of cm ³ expressed at a flow rate of gas supplied per minute of 0 ° C. and 1 atm = 1.69 × 10 ⁻³ Pa · m ³ / s (at 0 ° C.). The reason why the oxygen gas flow rate is set to 20 sccm or less is to maximize the reduction rate of the sputtering rate caused by the oxidation of the surface of the W target. “Sputtering rate” refers to the ratio of the number of sputtered atoms emitted per impact ion that bombards the sputter target.

  FIG. 3A shows the discharge characteristic of the W target when nitrogen is introduced (discharge characteristic of WN), and FIG. 3B shows the discharge characteristic of the W target when the nitrogen flow rate is fixed at 15 sccm and oxygen is introduced at 0 sccm to 50 sccm (WON Discharge characteristics). From the discharge characteristics of the W target in FIG. 3A, it can be seen that the discharge voltage gradually increases when the nitrogen flow rate is increased. On the other hand, from the discharge characteristics of the W target in FIG. 3B, when the oxygen flow rate is increased, the discharge voltage increases in the region where the oxygen flow rate is 30 sccm or less, but when the oxygen flow rate is further increased from 30 sccm, the discharge voltage gradually decreases. This change in the discharge voltage is because the surface of the metal target is oxidized and the sputtering rate is changed when the supply amount of oxygen is increased.

  FIG. 4A shows the nitrogen flow rate dependence on the WN film deposition rate, and FIG. 4B shows the oxygen flow rate dependence on the WON film and WO film deposition rates. In FIG. 4A, the plot of the black diamond “♦” indicates the result of the WN film. In FIG. 4B, the black circle “●” plots show the results for the WO film, and the black triangle “▲” plots show the results for the WON film. From FIG. 4A, it can be seen that the deposition rate of WN decreases as the nitrogen flow rate increases. The change in the discharge voltage is because the surface of the metal target is nitrided and the sputtering rate is lowered when the supply amount of nitrogen is increased. On the other hand, in FIG. 4B, the film formation rates of the WO and WON films increase as the oxygen flow rate increases. In order to realize the formation of the insulator film in one embodiment of the present invention without causing a decrease in the deposition rate, it is preferable to perform at least 15 sccm at which the nitriding of the W target is small.

  FIG. 5 shows the oxygen molar ratio O / (O + N + W) of the WON film and the oxygen gas flow rate dependency during the film formation. The composition was evaluated by AES (Auger Electron Spectroscopy Auger Electron Spectroscopy). From the result of the evaluation, it can be confirmed that the oxygen molar ratio is controlled in the range of 0 to 0.55 by adjusting the oxygen gas flow rate in the range of 0 sccm to 10 sccm.

  FIG. 6 shows the relationship between the specific resistance of the WON film and the molar ratio O / (O + N + W) of oxygen. The specific resistance of the WON film increases as the molar ratio of oxygen increases. When a WON film is used as the electrode film 5, it is desirable that the specific resistance of the electrode film 5 be 6000 μΩ · cm or less. Therefore, it is preferable to set the molar ratio of oxygen in the WON film in one embodiment of the present invention within the range of 0 to 0.22.

  FIG. 7 shows the relationship between the density of the WON film and the molar ratio O / (O + N + W) of oxygen. From the figure, it can be seen that the density of the WON film decreases as the oxygen molar ratio increases. When the density of the WON film decreases, the oxygen molar ratio of the WON film changes due to the diffusion of oxygen from the insulating film or the dielectric film, making it difficult to control the specific resistance. Therefore, it is necessary to control the oxygen molar ratio of the WON film in the range of 0 to 0.3 without greatly reducing the density, and the molar ratio O / of oxygen that can obtain a density of 10 g / cc or more is required. (O + N + W) is preferably controlled in the range of 0 <O / (O + N + W) ≦ 0.22. In addition, the measurement of the density was performed using XRR (X-RAY Reflectometer X-ray reflectivity method).

In order to measure the work function of WN film and WON film, 10 nm on SiO ₂ substrate
A stack structure was formed by laminating a TiN film, a 15 nm WN film or a 15 nm WON, and a 3 nm HfOx, and the electrical characteristics were measured. Note that the “work function” in this specification refers to the energy required to extract one electron from the Fermi level to the vacuum level. The work function was measured using a CV measuring device. FIG. 8 shows the relationship between the work function of WON and the molar ratio O / (O + N + W) of oxygen. The work function of the WON film increases as the molar ratio of oxygen increases, but has a maximum value, and 4.9 eV was obtained by setting the molar ratio of oxygen to 0.14. In order to realize a work function of 4.75 eV or more, it is necessary to control the molar ratio of oxygen in the range of 0 to 0.3, and preferably the molar ratio of oxygen having a work function of 4.87 eV or more is It preferably has a range of 0 <O / (O + N + W) ≦ 0.22.

Next, in order to prevent or reduce the change in O concentration in the WON film due to atmospheric exposure, the TiN film was capned and the composition of the WON film was measured.
FIGS. 9 and 10 show the composition in the film thickness direction after heat treatment of the laminated film of TiN film / WN film and TiN film / WON film at 1000 ° C., respectively. The composition was evaluated by SIMS (Secondary ionmass spectrometry secondary ion mass spectrometry). From FIG. 9, it can be seen that the TiN / WN laminated film is separated into two layers without diffusion of the metals of the TiN film and the WN film even after heat treatment at 1000 ° C. On the other hand, it can be seen from FIG. 10 that the TiN / WON laminated film is subjected to heat treatment at 1000 ° C., whereby Ti and W are interdiffused and the TiN / WON interface is unclear. From the above results, it is understood that when a metal film is laminated on WON and further heat treatment is applied, interdiffusion of W and metal can be suppressed by inserting a WN film between WON and the metal film. That is, when a TiN layer or the like is formed on a WON film by forming a WN film as a metal nitride layer containing W and N on the WON film as a gate electrode film, a TiN layer of W And diffusion of Ti into the WON film can be reduced.

Further, the step of forming the metal oxynitride is performed in the vacuum vessel 100 shown in FIG. 2 in the mixed atmosphere of the reactive gas 205 and the inert gas 201 made of a mixed gas of oxygen and nitrogen. This is a step of magnetron sputtering the metal targets 106 and 126 for forming. In this step, in order to suppress a decrease in the deposition rate, the supply amount of the reactive gas 205 is the supply amount that maximizes the reduction rate of the sputtering rate caused by oxidizing, nitriding or oxynitriding the surfaces of the metal targets 106 and 126. It is preferable to set the following. Further, in order to make the film thickness uniformity of the formed electrode film ± 2.5% or less, it is preferable to set the pressure in the vacuum vessel 100 during film formation to 1 × 10 ⁻¹ Pa or less.
In the case of forming a metal nitride layer containing W and N, the step of forming the metal oxynitride layer and the step of forming the metal nitride layer are performed in a vacuum without exposing the substrate to the atmosphere. It is preferable to carry out continuously.

In the above description, the charge trap type memory device in which the SiO ₂ layer 2 and the SiN layer 3 are stacked on the silicon oxide film 1 and the dielectric film 4 is deposited and then the electrode film 5 is formed will be described. However, it is not limited to these. For example, the metal oxynitride layer containing W, N, and O of the present invention is applied to an electrode film in a TANOS type nonvolatile memory, a floating electrode and a gate electrode in an FG type nonvolatile memory element, and a part of a MOS transistor. Thus, the effect can be sufficiently obtained.
That is, the method of the present invention (a step of forming a metal oxynitride layer containing W, N, and O as an electrode layer) can be applied to a method for manufacturing a semiconductor device having an electrode film. The manufacturing method of these is mentioned.
1. The method of the present invention includes a substrate having at least a surface composed of a semiconductor layer, a gate electrode formed on the substrate, and a stacked gate insulating film sequentially stacked between the substrate and the gate electrode. The present invention can be applied to a method for manufacturing a nonvolatile semiconductor device. That is, at least one insulating film included in the stacked gate insulating film is formed by the method of the present invention.
2. In one embodiment of the present invention, a substrate having at least a surface formed of a semiconductor layer, a gate electrode formed on the substrate, an insulating film, a floating electrode, and an insulating film between the substrate and the gate electrode In which the gate electrode and the floating electrode are at least partially formed of the electrode film of the present invention (a metal oxynitride layer containing W, N, and O) The non-volatile semiconductor device is also included.

(First Example: Example by Sputtering Method)
A first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 11 shows a MIS (metal insulator semiconductor) capacitor having a dielectric film 303. After a HfOx film was deposited as a dielectric film 303 on a silicon substrate 301 having a silicon oxide film 302 with a thickness of 3 nm to 5 nm on the surface, a WON film was deposited as an electrode film 304 by a sputtering method. A W metal target was used as the target, and argon, oxygen, and nitrogen were used as the sputtering gas. In FIG. 11, in order to prevent or reduce the change in O concentration in the WON film due to atmospheric exposure, when a TiN film is stacked on the WON film and heat treatment is performed, the WN is interposed between the WON film and the TiN film. A membrane may be inserted.

  The substrate temperature is 27 ° C. to 600 ° C., the target power is 50 W to 1000 W, the sputtering gas pressure is 0.02 Pa to 0.1 Pa, the Ar gas flow rate is 1 sccm to 200 sccm, the oxygen gas flow rate is 1 sccm to 100 sccm, and the nitrogen gas flow rate is 1 sccm to It can be determined as appropriate within the range of 100 sccm.

  Here, the film was formed at a substrate temperature of 30 ° C., a Hf target power of 500 W, a sputtering gas pressure of 0.03 Pa, an Ar gas flow rate of 25 sccm, and an oxygen flow rate of 0 sccm to 20 sccm.

  At this time, the oxygen molar ratio O / (Hf + O) of the dielectric film 303 can be controlled by the Hf target power and the oxygen flow rate.

  As the dielectric film 303, a dielectric film 303 as a HfOx film having an oxygen molar ratio in the range of 0 ≦ O / (Hf + O) ≦ 0.50 using the above-described formation step was formed in a thickness range of 5 nm to 25 nm. .

Although the HfOx film is used here as the dielectric film 303, Al ₂ O ₃ and HfAlON can also be used as appropriate. Further, a film selected from the group consisting of these may be deposited.

  The electrode film 304 was formed at a substrate temperature of 30 ° C., a target power of 500 W at W, a sputtering gas pressure of 0.03 Pa, an Ar gas flow rate of 25 sccm, a nitrogen flow rate of 15 sccm, and an oxygen flow rate of 0 sccm to 50 sccm.

At this time, the molar ratio O / (O + N + W) of the electrode film 304 of the present embodiment can be controlled by the W target power, the O flow rate, and the N flow rate. FIG. 5 shows the oxygen flow rate dependency of the molar ratio O / (O + N + W) of the electrode film 304 formed in this example. The composition is AES (AugerElectron
(Evaluation by spectroscopic Auger electron spectroscopy). Thus, it was confirmed that the molar ratio O / (O + N + W) could be controlled in the range of 0 to 0.3 by adjusting the oxygen flow rate.

  Next, annealing was performed for 10 seconds at a temperature of 1000 ° C. in a nitrogen atmosphere to crystallize the dielectric film 303. Although the annealing process is performed after the electrode film (WON film) 304 is deposited here, the annealing process may be performed before the electrode film (WON film) 304 is deposited. Further, although the annealing treatment is performed here in a nitrogen atmosphere, an oxygen atmosphere or an inert gas atmosphere such as Ar can be used as appropriate. Moreover, you may anneal in the atmosphere selected from the group which consists of these.

  Next, the electrode film (WON film) 304 was processed into a desired size using a lithography technique and an RIE technique to form a MIS capacitor structure.

  The specific resistance of the electrode film (WON film) 304 produced as described above was evaluated. From the relationship between the molar ratio of oxygen and the specific resistance of the WON film shown in FIG. 6, the specific resistance is 6000 μΩ · cm or less in the range of the molar ratio of oxygen 0 <(O / (O + N + W)) ≦ 2.2.

  FIG. 7 shows the relationship between the density of WON and the molar ratio of oxygen O / (O + N + W). From the figure, it can be seen that the density of WON decreases as the molar ratio of oxygen increases.

  FIG. 8 shows the relationship between the work function of WON and the molar ratio O / (O + N + W) of oxygen. The work function of WON increases as the oxygen content increases, but has a maximum value, and 4.9 eV was obtained by setting the molar ratio of oxygen to 0.14. In order to realize a work function of 4.75 eV or more, it is necessary to control the molar ratio of oxygen in the range of 0 to 0.3, and preferably the molar ratio of work function of 4.87 eV or more is from 0 to 0. It is preferable to control within the range of 0.22.

As can be seen from the above, according to this example, the electrode film is composed of a composite oxynitride containing W, N, and O, and the molar ratio O / (O + N + W) of W, O, and N is 0. In an electrode film having a film formation rate of 5 nm / min or more and a film density of 10 g / cm ³ or more, a work function of 4.9 eV or more can be obtained. Recognize.

(Second Embodiment: Embodiment Applied to Electrode Film of Nonvolatile Memory Element)
FIG. 12 is a cross-sectional view showing a manufacturing process of a semiconductor device according to the second embodiment of the present invention.

  First, as shown in Step 121 of FIG. 12, an element isolation region 402 was formed on the surface of the silicon substrate 401 by using STI (Shallow Trench Isolation) technology.

  Subsequently, a silicon oxide film was formed as a first insulating film 403 on the surface of the isolated silicon substrate 401 by a thermal oxide film method by 30 to 100 mm. Subsequently, a silicon nitride film was formed as the second insulating film 404 by 30 to 100 by LPCVD (Low Pressure Chemical Vapor Deposition). Subsequently, an aluminum oxide film having a thickness of 5 to 50 mm was formed as the third insulating film 405. The aluminum oxide film may be formed by MOCVD, ALD (Atomic Layer Deposition), or PVD (Physical Vapor Deposition). Subsequently, an HfAlON film having a thickness of 5 nm to 20 nm was formed as the fourth insulating film 406. Subsequently, an aluminum oxide film having a thickness of 5 to 50 mm was formed as the fifth insulating film 407. As a forming method, MOCVD method, ALD method, and PVD method were used.

  Next, a WON film having a thickness of 10 nm was formed as the gate electrode 408. The WON film was created using the PVD method. After the fabrication of the gate electrode, as shown in Step 122 of FIG. 12, the gate electrode is processed using lithography technology and RIE (Reactive Ion Etching) technology, and then ion implantation is performed, and the extension region 409 is masked with the gate electrode. As self-aligned. Furthermore, as shown in step 123 of FIG. 12, a gate sidewall 410 is formed by sequentially depositing a silicon nitride film and a silicon oxide film and then etching back. In this state, ion implantation was performed again, and source / drain regions 411 were formed through activation annealing. In FIG. 12, in order to prevent or reduce the change in O concentration in the WON film due to exposure to the atmosphere, when a TiN film is stacked on the WON film and heat treatment is performed, the WN is interposed between the WON film and the TiN film. A membrane may be inserted.

  The work function of the electrode film 408 manufactured as described above and the reliability of the semiconductor element were evaluated.

  From the relationship between the work function of WON and the molar ratio of oxygen O / (O + N + W) shown in FIG. 8, the work function of WON increases as the molar ratio of oxygen increases, but has a maximum value, and the molar ratio of oxygen increases. By setting it to 0.14, 4.9 eV was obtained.

  Table 1 below shows the relationship between leakage current and reliability for various upper electrode films. In Table 1 below, “Top electrode” is the gate electrode, “Program ΔVfb” is the voltage difference between writing and erasing, “Retention% Vfb change” is reliability, “CET” is the equivalent oxide film thickness, “J at” indicates an applied voltage.

  From Table 1 above, when the WON film is a gate electrode, the leakage current (0.00019) at an applied voltage of 20 V (J at 20 V) is the leakage current of the TiN electrode (0.0003) or the leakage current of the WN electrode (0 It is found that the leakage current is further reduced when the molar ratio of oxygen is increased. In addition, when the WON film having a molar ratio of oxygen having a maximum work function of 0.14 is used as an electrode, the reliability is improved, and the Vfbchange ratio is 5.41%, which is more than double that when a TiN film is used. The improvement was seen.

  Thus, according to this example, WON (molar ratio of oxygen 0 <(O / (O + N + W) ≦ 0.3) is represented, and the work function is 4.9 eV or more by performing sputtering, and It was confirmed that an electrode film capable of reducing the leakage current value and improving the reliability was obtained, wherein Fig. 13 is a cross-sectional view of the semiconductor device of Example 2, and 601 represents poly-Si.

(Third embodiment: an embodiment applied to an electrode film of a stacked gate type memory cell)
The electrode film of the present invention can also be applied to a floating gate FG or a control gate CG of a known stacked gate type memory cell. By applying the electrode film of the present invention to the floating gate FG or the control gate CG, the work function is 4.9 eV or more, the leakage current value is reduced, and the reliability can be improved. It was confirmed that a gate CG was obtained.

Claims (3)

On the silicon substrate, a tunnel oxide film, a charge trap film, a blocking insulating film, and a gate electrode have a laminated structure formed in this order, and by applying a voltage to the gate electrode, the silicon substrate side A charge trap memory device manufacturing method for writing and erasing information by trapping and detrapping charges in a charge trap film,
Preparing the silicon substrate on which the tunnel oxide film, the charge trap film, and the blocking insulating film are sequentially formed;
Forming a metal oxynitride layer containing W, N and O on the blocking insulating film;
Forming a metal nitride layer containing W and N on the metal oxynitride layer,
Forming the metal oxynitride layer and the metal nitride layer,
In a vacuum vessel, magnetron sputtering a metal target made of metal contained in the metal oxynitride layer and the metal nitride layer in a mixed atmosphere of a reactive gas and an inert gas,
The reactive gas in the step of forming the metal oxynitride layer is oxygen and nitrogen;
A method for manufacturing a charge trap memory device, wherein the reactive gas in the step of forming the metal nitride layer is nitrogen.   The magnetron sputtering step sets the supply amount of the reactive gas or the inert gas below the supply amount that maximizes the reduction rate of the sputtering rate caused by oxidation, nitridation, or oxynitridation of the surface of the metal target. The method of manufacturing a charge trap memory device according to claim 1. 2. The method for manufacturing a charge trap memory device according to claim 1, wherein the pressure in the vacuum vessel is set to 1 × 10 ⁻¹ Pa or less.

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