JP5462897B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  Conventionally, in the technical field related to semiconductor devices, a so-called charge trap type having a laminated structure in which a tunnel oxide film, a charge trap film, a blocking oxide film, and a gate electrode are formed in this order from the lower side on a silicon substrate. Non-volatile memory devices (flash memories) are known.

Such charge trap type nonvolatile memory devices include SONOS structure (polysilicon film, SiO ₂ (amorphous) film, SiN film, SiO ₂ film, laminated structure of silicon substrate), SANOS structure (polysilicon film, Al ₂ O ₃ (crystalline) film, SiN film, SiO ₂ film, laminated structure of silicon substrate), TANOS structure (TaN film, Al ₂ O ₃ (crystalline) film, TaN film, SiO ₂ film, laminated structure of silicon substrate) Structures), MANOS structures (metal films, Al ₂ O ₃ (crystalline) films, TaN films, SiO ₂ films, laminated structures of silicon substrates) and the like are known.

As described above, in the conventional charge trap type nonvolatile memory device, as a blocking oxide film, an SiO ₂ (amorphous) film, an Al ₂ O ₃ (crystalline) film, or a high dielectric constant film (HfO ₂ film ( (See, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

No. 2006-203200 2008-16814 2008-34814 publication

As described above, when a SiO ₂ (amorphous) film is used as the blocking oxide film, when data is erased by injecting holes into the charge trapping film from the silicon substrate side, writing by electrons from the gate electrode side is performed. As a result, there is a problem that the window characteristics on the erase side deteriorate.

On the other hand, when an Al ₂ O ₃ (crystalline) film or a high dielectric constant film (HfO ₂ film (crystalline)) is used as the blocking oxide film, hole traps are formed in the film by crystallization. Therefore, the window characteristic on the erase side is improved. However, since a leakage path is formed in the film by crystallization, electron leakage from the charge trapping film occurs, and there is a problem that the retention characteristic is deteriorated.

  The present invention has been made in view of the above-described conventional circumstances, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of simultaneously improving the window characteristics and the retention characteristics.

One aspect of the method for manufacturing the semiconductor device of the present invention, on a silicon substrate, a tunnel oxide film, a charge trap film, blocking oxide film, a gate electrode, a semiconductor device having a laminated structure formed in this order from the bottom side In the manufacturing method, the step of forming the blocking oxide film includes a first amorphous film forming step of forming a first amorphous film on the charge trap film, and the first amorphous film on the first amorphous film. A second amorphous film forming step of forming a second amorphous film that is less likely to be crystallized; and heating to a temperature at which the first amorphous film is crystallized and the second amorphous film is not crystallized. A heating step for crystallizing the amorphous film, and the first amorphous film forming step and the second amorphous film forming step. Characterized by continuously carrying out the said heating step in the same process vessel.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the semiconductor device which can aim at the improvement of a window characteristic and the improvement of a retention characteristic simultaneously can be provided.

The figure which shows typically the principal part cross-section structure of the semiconductor device of one Embodiment of this invention. The figure which shows the window characteristic of an amorphous film. The figure which shows the window characteristic of a crystalline film. The figure which shows the retention characteristic of an amorphous film and a crystalline film. The figure which shows typically the longitudinal cross-section structure of the manufacturing apparatus of the semiconductor device for performing the method of one Embodiment of this invention. The figure which shows typically the cross-sectional structure of the manufacturing apparatus of the semiconductor device of FIG. The figure for demonstrating the process of the manufacturing method of the semiconductor device of one Embodiment of this invention. The figure which shows typically the principal part cross-section structure of the semiconductor device of other embodiment of this invention.

  Hereinafter, details of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an enlarged main part configuration of a semiconductor device (charge trap type nonvolatile memory device (flash memory)) according to an embodiment of the present invention. As shown in the figure, in the semiconductor device 100 of this embodiment, a tunnel oxide film 111, a charge trap film 112, a blocking oxide film 113, and a gate electrode 114 are formed in this order from below on a silicon substrate 110. Have a laminated structure.

The tunnel oxide film 111 is composed of a silicon oxide film (SiO ₂ film), and the charge trap film 112 is composed of a silicon nitride film (SiN film).

The blocking oxide film 113 has a two-layer structure, and is composed of a crystalline film 113a formed on the charge trap film 112 side and an amorphous film (amorphous film) 113b formed on the gate electrode 114 side. It is configured. As the crystalline film 113a, for example, a crystallized alumina film (Al ₂ O ₃ film) or a crystallized high dielectric constant film (High-k film), for example, HfO ₂ , ZrO ₂ , Ta ₂ O _{5 is used.} , Y ₂ O ₃ , lanthanoid oxides, and the like. The amorphous film 113b can be composed of, for example, an HTO (high temperature oxidation) film (SiO ₂ film), an aluminum silicate film, an amorphous-Al ₂ O ₃ film, an Al ₂ O ₃ —SiO ₂ laminate film, or the like. .

  The gate electrode 114 can be composed of a polysilicon film, a TaN film, a metal film, or the like.

2 and 3, the vertical axis represents capacitance (C (F / cm ² )) and the horizontal axis represents gate voltage Vg (V), and an amorphous film (amorphous-Al ₂ O ₃ film) and a crystalline film (crystalline) This shows the results of examining the window characteristics of the (-Al ₂ O ₃ film). In FIGS. 2 and 3, the square mark plot indicates initial, the circular mark plot indicates program (write), and the triangle plot indicates erase (erase). As shown in FIG. 3, when the crystalline film is used as the blocking oxide film 113, the window characteristic on the erase side is improved compared to the case of the amorphous film shown in FIG. 2 (ΔV = 3.4V), The window characteristic becomes good at ΔV = 8.2V. This is because hole traps are formed in the film by crystallization.

On the other hand, in FIG. 4, the vertical axis is ΔVFB (V) and the horizontal axis is the retention time (s), and an amorphous film (amorphous-Al ₂ O ₃ film) (shown by a circular mark in the figure) and crystalline It shows the result of examining the retention characteristics of the film (crystalline-Al ₂ O ₃ film) (indicated by a triangular mark in the figure). As shown in the figure, the amorphous film shows good retention characteristics. However, in the case of a crystalline film, electrons escape from the charge trap film 112 and the retention characteristics deteriorate.

  As described above, when an amorphous film is used as the blocking oxide film 113, the retention characteristic is improved, but the window characteristic is deteriorated. On the other hand, when a crystalline film is used as the blocking oxide film 113, the window characteristic is improved, but the retention characteristic is deteriorated. For this reason, in the present embodiment, a crystalline film 113a with good window characteristics is provided on the charge trap film 112 side, and an amorphous film 113b capable of improving retention characteristics is formed on the gate electrode 114 side, thus blocking the two-layer structure. By using the oxide film 113, a semiconductor device having good window characteristics and retention characteristics can be obtained.

  In the above embodiment, the blocking oxide film 113 has a two-layer structure of the crystalline film 113a and the amorphous film 113b. However, the blocking oxide film 113 is crystalline on the charge trap film 112 side and is directed to the gate electrode 114 side. Accordingly, a film having a structure that gradually becomes amorphous can be used.

  Next, a method for manufacturing the semiconductor device having the above configuration will be described. FIG. 5 is a diagram showing a schematic vertical cross-sectional configuration of a semiconductor device manufacturing apparatus (film forming apparatus) used in an embodiment of a semiconductor device manufacturing method of the present invention, and FIG. 6 is a cross-sectional schematic configuration (heating means). Is omitted).

  As shown in FIG. 5, the film forming apparatus 2 capable of forming plasma has a cylindrical processing container 4 having a ceiling with a lower end opened. The entire processing container 4 is made of, for example, quartz, and a ceiling plate 6 made of quartz is provided on the ceiling in the processing container 4 and sealed. Further, a manifold 8 formed in a cylindrical shape by, for example, stainless steel is connected to a lower end opening of the processing container 4 via a seal member 10 such as an O-ring.

  The lower end of the processing vessel 4 is supported by the manifold 8, and a quartz wafer boat 12 as a holding means on which a plurality of semiconductor wafers W as processing objects are placed in multiple stages from below the manifold 8. Is made detachable so that it can be raised and lowered. In the case of the present embodiment, for example, about 50 to 100 wafers 300 having a diameter of 300 mm can be supported in multiple stages at substantially equal pitches on the support 12A of the wafer boat 12.

  The wafer boat 12 is placed on a table 16 via a quartz heat insulating cylinder 14, and the table 16 penetrates a lid 18 made of, for example, stainless steel that opens and closes the lower end opening of the manifold 8. It is supported on the rotating shaft 20. For example, a magnetic fluid seal 22 is interposed in the penetrating portion of the rotating shaft 20, and the rotating shaft 20 is rotatably supported while hermetically sealing. In addition, a sealing member 24 made of, for example, an O-ring is interposed between the peripheral portion of the lid portion 18 and the lower end portion of the manifold 8 to maintain the sealing performance in the processing container 4.

  The rotating shaft 20 is attached to the tip of an arm 26 supported by an elevating mechanism (not shown) such as a boat elevator, for example, and moves up and down integrally with the wafer boat 12, the lid 18 and the like. 4 can be inserted and removed.

The manifold 8 includes a support gas supply means 28 for supplying a support gas to be converted into plasma toward the inside of the processing container 4, a source gas supply means 30 for supplying a source gas, and an inert gas such as N ₂ gas as a purge gas. Purge gas supply means 32 is provided. Specifically, the support gas supply means 28 has a support gas dispersion nozzle 34 made of a quartz tube that extends through the side wall of the manifold 8 inward and is bent upward. A plurality (a large number) of gas injection holes 34A are formed at predetermined intervals along the length direction of the assist gas dispersion nozzle 34, and are substantially uniform from the gas injection holes 34A in the horizontal direction. It is possible to inject support gas.

  Similarly, the source gas supply means 30 also has a source gas dispersion nozzle 36 made of a quartz tube that penetrates the side wall of the manifold 8 inward and bends and extends upward. As shown in FIG. 6, two source gas dispersion nozzles 36 are provided. Each source gas dispersion nozzle 36 is formed with a plurality of (many) gas injection holes 36A at predetermined intervals along the length direction thereof, and is substantially uniform from each gas injection hole 36A in the horizontal direction. The material gas can be injected into the tank. Similarly, the purge gas supply means 32 has a gas nozzle 38 provided through the side wall of the manifold 8. Respective gas passages 42, 44, 46 are connected to the nozzles 34, 36, 38.

  The gas passages 42, 44, 46 are respectively provided with on-off valves 42A, 44A, 46A and flow rate controllers 42B, 44B, 46B such as a mass flow controller, for supporting gas, raw material gas and inert gas. Each can be supplied while controlling the flow rate. Supply of these gases, supply stop, control of gas flow rate, high frequency on / off control described later, and the like are performed by a control means 48 including, for example, a microcomputer. The control unit 48 also controls the overall operation of the film forming apparatus 2. The control means 48 also stores a storage medium 49 such as a floppy disk or a flash memory for storing programs for controlling the supply and stop of the various gases, high-frequency on / off control, and operation of the entire apparatus. Have.

  An activation means 50 is formed on a part of the side wall of the processing container 4 to generate plasma along the height direction thereof to activate the support gas, and the processing container facing the activation means 50 is formed. On the opposite side of 4, an elongated exhaust port 52 formed by scraping the side wall of the processing container 4 in the vertical direction, for example, is provided in order to evacuate the internal atmosphere. Specifically, the activation means 50 forms an elongated opening 54 in the vertical direction by scraping the side wall of the processing container 4 with a predetermined width along the vertical direction, and covers the opening 54 from the outside. In this way, a plasma partition wall 56 made of, for example, quartz, which is vertically concave and downward in a cross-sectional recess shape, is hermetically welded to the outer wall of the container. As a result, a part of the side wall of the processing container 4 is recessed outward in the shape of a recess so that the activating means 50 having one side opened into the processing container 4 and communicated therewith is integrally formed. That is, the internal space of the plasma partition wall 56 is in a state of being integrally communicated with the processing container 4. The opening 54 is formed long enough in the vertical direction so as to cover all the wafers W held by the wafer boat 12 in the height direction.

  A pair of elongate plasma electrodes 58 are provided on the outer surfaces of both side walls of the plasma partition wall 56 so as to face each other along the length direction (vertical direction). A high frequency power supply 60 is connected via a power supply line 62, and plasma can be generated by applying a high frequency voltage of 13.56 MHz to the plasma electrode 58, for example. The frequency of the high-frequency voltage is not limited to 13.56 MHz, and other frequencies such as 400 kHz may be used. The assist gas dispersion nozzle 34 extending upward in the processing container 4 is bent outward in the radial direction of the processing container 4 in the middle, and is located farthest inside the plasma partition wall 56 (from the center of the processing container 4). It is located at the farthest part) and is provided to stand upward along this innermost part. Therefore, when the high-frequency power source 60 is turned on, the support gas injected from the gas injection hole 34A of the support gas dispersion nozzle 34 is activated here and flows while diffusing toward the center of the processing container 4. ing.

  An insulating protective cover 64 made of, for example, quartz is attached to the outside of the plasma partition wall 56 so as to cover it. In addition, a refrigerant passage (not shown) is provided in an inner portion of the insulating protective cover 64 so that the plasma electrode 58 can be cooled by flowing a cooled nitrogen gas. The two source gas dispersion nozzles 36 are provided upright in the vicinity of the outside of the opening 54 of the plasma partition wall 56, that is, on both sides outside the opening 54 (inside the processing vessel 4). The raw material gas can be injected from the gas injection holes 36 </ b> A toward the center of the processing container 4.

  On the other hand, an exhaust port cover member 66 formed in a U-shaped cross section made of quartz is attached to the exhaust port 52 provided to face the opening 54 by welding so as to cover it. The exhaust port cover member 66 extends upward along the side wall of the processing vessel 4 and is evacuated from a gas outlet 68 above the processing vessel 4 by a vacuum exhaust system provided with a vacuum pump (not shown). . A cylindrical heating means 70 for heating the processing container 4 and the wafer W inside the processing container 4 is provided so as to surround the outer periphery of the processing container 4.

  Next, a method for manufacturing the semiconductor device of the present embodiment using ALD film formation performed using the film formation apparatus configured as described above will be described. In this case, first, the wafer boat 12 on which a large number of normal temperature wafers, for example, 50 to 100 wafers 300 mm in size are placed, is raised from below in the processing container 4 that has been previously set to a predetermined temperature. The container is sealed by closing the lower end opening of the manifold 8 with the lid 18.

  Next, the inside of the processing container 4 is evacuated and maintained at a predetermined process pressure, and the power supplied to the heating means 70 is increased to increase the wafer temperature and maintain the process temperature. Are alternately and intermittently supplied from the source gas supply means 30 and the support gas supply means 28, and a thin film is sequentially formed on the surface of the wafer W supported by the rotating wafer boat 12. At this time, the high frequency power source (RF power source) 60 is turned on to generate plasma.

  In this embodiment, as shown in FIG. 1, a tunnel oxide film 111 and a charge trap film 112 are sequentially formed on a silicon substrate 110, and then a blocking oxide film 113 is formed. At this time, for example, TMA gas and oxygen gas, which is a support gas, are intermittently supplied alternately as a raw material gas and activated by plasma.

Then, as shown in FIG. 7, first, an amorphous-Al ₂ O ₃ film is formed at a temperature of about 200 to 600 ° C., and then the temperature in the processing container 4 is once increased to 750 to 1000 ° C. Annealing (heat treatment) is performed to crystallize the amorphous-Al ₂ O ₃ film. Thereby, the crystalline film 113a is formed.

Next, the temperature is lowered again to a temperature of about 200 to 600 ° C. to form an amorphous film, for example, an amorphous-Al ₂ O ₃ film. As a result, the blocking oxide film 113 composed of two layers of the crystalline film 113a and the amorphous film 113b can be formed. As described above, in this embodiment, the blocking oxide film 113 composed of the two layers of the crystalline film 113a and the amorphous film 113b can be simultaneously formed on many wafers W in the same processing container 4.

Incidentally, the crystalline film 113a, in addition to crystalline _-Al 2 _{O 3} film, for example, crystalline -HfO ₂ film, crystalline -ZrO ₂ film, crystalline _-Ta 2 _{O 5} film, a crystalline _-Y 2 O _Three films, a crystalline-lanthanoid oxide film, and the like may be used. In addition, the amorphous film 113b is not limited to the amorphous-Al ₂ O ₃ film, and for example, any of an amorphous-SiO ₂ film, an amorphous-aluminum silicate film, an amorphous-Al ₂ O ₃ -SiO ₂ laminate film, etc. It is good.

In the above embodiment, after the amorphous film is crystallized to form a crystalline film 113a, it was an amorphous film 113b, for example, after forming the amorphous _-Al 2 _{O 3} film, difficult to crystallize than _{the Al} 2 _{O 3} film A film, for example, an SiO ₂ film, an aluminum silicate film, an Al ₂ O ₃ —SiO ₂ laminate film, etc. is formed, and thereafter, an amorphous-Al ₂ O ₃ film is crystallized to obtain an SiO ₂ film, an aluminum silicate film, an Al _The blocking oxide film 113 formed of two layers of the crystalline film 113a and the amorphous film 113b may be formed by annealing at a temperature at which the ₂ O ₃ —SiO ₂ laminate film or the like is not crystallized.

Further, the Al ₂ O ₃ —SiO ₂ laminate film is laminated while changing the ratio thereof, and a laminate film is formed in which the ratio of Al ₂ O ₃ is gradually decreased and the ratio of SiO ₂ is gradually increased. By performing the crystallization, only the portion having a high proportion of Al ₂ O ₃ which is easily crystallized is crystallized, and the portion having a high proportion of SiO ₂ is left in an amorphous state, whereby blocking oxidation comprising the crystalline film 113a and the amorphous film 113b is performed. The film 113 may be formed.

  Furthermore, an aluminum silicate film is formed while changing the ratio of aluminum and silicon, an aluminum silicate film is formed by gradually decreasing the ratio of aluminum and increasing the ratio of silicon, and then performing a heat treatment to thereby form aluminum silicate film. The blocking oxide film 113 composed of the crystalline film 113a and the amorphous film 113b may be formed by crystallizing only the portion that contains a large amount of crystallized and crystallizing only the portion that contains a large amount of silicon, and the portion that does not crystallize a lot containing silicon. .

  Next, a semiconductor device (charge trap type nonvolatile memory device (flash memory)) according to another embodiment will be described with reference to FIG. FIG. 8 schematically shows an enlarged configuration of a main part of the semiconductor device according to the present embodiment. As shown in the figure, in the semiconductor device 200 of this embodiment, a tunnel oxide film 211, a charge trap film 212, a blocking oxide film 213, and a gate electrode 214 are formed in this order from the lower side on a silicon substrate 210. Have a laminated structure.

The tunnel oxide film 211 is composed of a silicon oxide film (SiO ₂ film). The charge trap film 212 is formed of a crystalline film, and the blocking oxide film 213 is formed of an amorphous film (amorphous film). Examples of the crystalline film constituting the charge trap film 212 include a crystallized alumina film (Al ₂ O ₃ film) or a crystallized high dielectric constant film (High-k film) such as HfO ₂ and ZrO _2. , Ta ₂ O ₅ , Y ₂ O ₃ , lanthanoid oxides, and the like can be used. Examples of the amorphous film constituting the blocking oxide film 213 include an HTO (high temperature oxidation) film (SiO ₂ film), an aluminum silicate film, an amorphous-Al ₂ O ₃ film, an Al ₂ O ₃ —SiO ₂ laminate film, and the like. Can be used.

  The gate electrode 114 can be composed of a polysilicon film, a TaN film, a metal film, or the like.

  As in the semiconductor device 200 of this embodiment, the charge trap film 212 can be formed of a crystalline film, and the blocking oxide film 213 can be formed of an amorphous film (amorphous film). Further, such a laminated structure can be manufactured using the apparatus shown in FIGS. 5 and 6 in the same manner as in the above-described embodiment.

  As described above, according to the present embodiment, it is possible to provide a method of manufacturing a semiconductor device that can simultaneously improve the window characteristics and the retention characteristics.

  DESCRIPTION OF SYMBOLS 100 ... Semiconductor device, 110 ... Silicon substrate, 111 ... Tunnel oxide film, 112 ... Charge trap film, 113 ... Blocking oxide film, 113a ... Crystalline film, 113b ... Amorphous film, 114 ... Gate electrode.

Claims (6)

A method of manufacturing a semiconductor device having a stacked structure in which a tunnel oxide film, a charge trap film, a blocking oxide film, and a gate electrode are formed in this order from the lower side on a silicon substrate,
Forming the blocking oxide film comprises:
A first amorphous film forming step of forming a first amorphous film on the charge trap film;
Forming a second amorphous film on the first amorphous film, the second amorphous film being less crystallized than the first amorphous film;
Heating to a temperature at which the first amorphous film is crystallized and the second amorphous film is not crystallized to crystallize the first amorphous film, and
A method of manufacturing a semiconductor device, wherein the first amorphous film forming step, the second amorphous film forming step, and the heating step are continuously performed in the same processing container. A method of manufacturing a semiconductor device according to claim 1 ,
The first amorphous film forming step, the second amorphous film forming step, and the heating step are accommodated by stacking a plurality of the silicon substrates in a vertical direction in the cylindrical processing container. A method for manufacturing a semiconductor device, characterized in that the method is performed by a batch type processing apparatus. A method of manufacturing a semiconductor device according to claim 2 ,
The batch processing apparatus includes a mechanism for supplying a processing gas into the processing container, a mechanism for converting the processing gas into plasma, a mechanism for heating the silicon substrate, and a mechanism for evacuating the processing container. A method for manufacturing a semiconductor device, comprising: A method for manufacturing a semiconductor device according to any one of claims 1 to 3 ,
A method of manufacturing a semiconductor device, wherein the charge trap film is made of SiN. A method of manufacturing a semiconductor device according to any one of claims 1 to 4 ,
The method for manufacturing a semiconductor device, wherein the first amorphous film is made of any one of Al ₂ O ₃ , HfO ₂ , ZrO ₂ , Ta ₂ O ₅ , Y ₂ O ₃ , and a lanthanoid oxide. . A method for manufacturing a semiconductor device according to any one of claims 1 to 5 ,
The method of manufacturing a semiconductor device, wherein the second amorphous film is composed of any one of a SiO ₂ film, an aluminum silicate film, an Al ₂ O ₃ film, and an Al ₂ O ₃ —SiO ₂ laminate film.

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