JP2009132961A - Film-forming method, film-forming apparatus and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-forming method which can form a film of alumina including α-alumina at a lower film-forming temperature. <P>SOLUTION: This film-forming method includes: placing an article to be treated (wafer W) in a treating vessel 2; introducing a source gas containing an organoaluminum compound, and an oxidative gas containing a hydrogen atom and an oxygen atom such as vapor into the treating vessel 2; subsequently heating a treating atmosphere in the treating vessel 2 to a temperature range between 200°C and 500°C to form a film of an oxygen-containing aluminum compound including diaspore on the article to be treated; and heating the article to be treated in a temperature range between 800°C and 1,000°C to convert the film of the oxygen-containing aluminum compound into the film of alumina including α-alumina. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a film forming method for forming an alumina film containing α-alumina (α-Al ₂ O ₃ ; α-type aluminum oxide), a film forming apparatus, and a storage medium storing a program for executing the film forming method.

High integration and miniaturization of semiconductor devices are progressing, and device structures are also diversifying. With this trend, efforts are being made to select and develop more appropriate films in terms of characteristics and manufacturing processes. It has been poured.
For example, a memory element 100 used in a MONOS (Metal-Oxide-Nitride-Oxide-Semiconductor) type flash memory has a silicon layer (silicon substrate 110) between a source electrode 101 and a drain electrode 102 as shown in FIG. A tunnel oxide film 103, a charge trap layer 104, a blocking insulating layer 105, and a control gate 106 are stacked on top of each other (the memory element 100 in which the control gate 106 is formed of polysilicon is formed by SONOS (Silicon- Oxide-Nitride-Oxide-Semiconductor) type). The charge trap layer 104 is formed of, for example, a silicon nitride film (Si ₃ N ₄ ). As the blocking insulating layer 105, a film having a large band gap with respect to the silicon nitride film and a small leakage current is used.

  On the other hand, a conventionally used floating gate type flash memory is a so-called ONO film in which both sides of a silicon nitride film are sandwiched between silicon oxide films between a floating gate for storing charges and a control gate for applying a control voltage. Insulation is performed by a three-layer gate insulating film.

Recently, in the above-described MONOS type memory element 100, a technique using α-Al ₂ O ₃ as the blocking insulating layer 105 has been studied. α-Al ₂ O ₃ has a corundum crystal structure and is abundant in minerals, but its band gap is about 8.8 eV, which is large compared to silicon nitride film, and its dielectric constant is high. Since it can be increased, leakage current can be suppressed and the blocking insulating layer 105 can be preferably used. If α-Al ₂ O ₃ is used, the blocking insulating layer has a single-layer structure. Therefore, there is an advantage that the manufacturing process can be simplified as compared with a floating gate type flash memory in which an ONO film is used as the gate insulating film.

α-Al ₂ O ₃ is obtained, for example, by forming a film at a process temperature of about 300 ° C. using TMA (trimethylaluminum) as a raw material and then annealing at a high temperature of 1,100 ° C. or higher. Al ₂ O ₃ is amorphous at the stage of film formation at about 300 ° C., for a phase transition to the α-Al ₂ O ₃ type, it is necessary to anneal at a high temperature of at least 1,100 ° C.. When a film is formed at a temperature higher than 300 ° C. using TMA, the TMA supplied into the processing container in which the film is formed is thermally decomposed in the vapor phase before reaching the center of the semiconductor wafer, and the wall of the container Most of the film is consumed for adsorbing to the edge of the semiconductor wafer, and as a result, the film is formed only on the edge of the semiconductor wafer.

On the other hand, if the semiconductor wafer is annealed at a high temperature of 1,100 ° C., an unscheduled thermal history remains in the portion that has been laminated so far, and the activity of, for example, ion-implanted impurities changes from the design value. For this reason, the annealing temperature can only be set up to about 1,000 ° C. in an actual manufacturing process, but if so, crystals of a spinel structure such as γ-Al ₂ O ₃ , θ-Al ₂ O ₃ , η-Al ₂ O ₃ are formed. not only Al ₂ O ₃ containing, band gap of the silicon nitride film is as low as about 8.2EV, characteristics that are aimed by using α-Al ₂ O ₃ can not be obtained. Such process problems prevent the application of α-Al ₂ O ₃ in the MONOS structure of flash memory.

In Patent Document 1, aluminum chloride (AlCl ₃ ) and titanium chloride (TiCl ₄ ) are alternately reacted with water vapor in a processing vessel to form an ATO film in which alumina films and titanium oxide films are alternately stacked. A filming technique is described. However, this technique does not describe a technique for forming an alumina film containing α-Al ₂ O ₃ in particular, and cannot solve the above problem.
JP 2001-234345 A: 0026 paragraph

  The present invention has been made under such circumstances, and an object thereof is a film forming method, a film forming apparatus, and a film forming method capable of lowering the film forming temperature of an alumina film containing α-alumina. The object is to provide a storage medium storing a program for carrying out the method.

A method for forming an alumina film according to the present invention includes a step of placing an object to be processed in a processing container,
Introducing a raw material gas containing an organoaluminum compound into the processing vessel;
Introducing an oxidizing gas containing hydrogen atoms and oxygen atoms into the processing vessel;
By heating the processing atmosphere in the processing container in a temperature range of 200 ° C. or higher and 500 ° C. or lower, the raw material gas and the oxidizing gas are reacted to form an oxygen-containing aluminum compound containing diaspore on the surface of the object to be processed. Forming a film;
The object on which the oxygen-containing aluminum compound film is formed is heated in a temperature range of 800 ° C. or more and 1,000 ° C. or less, and the oxygen-containing aluminum compound film is converted into an alumina film containing α-alumina. And a step of changing. Furthermore, the step of introducing the source gas into the processing container and the step of introducing the oxidizing gas into the processing container are preferably performed alternately.

  In the film forming method, the organoaluminum compound preferably contains trimethylaluminum or tris (1-methoxy-2-methyl-2-propoxy) aluminum, and the oxidizing gas containing hydrogen atoms and oxygen atoms is Preference is given to an atom containing a hydroxy group, for example water vapor. The alumina film formed by this film forming method is preferably applied to a blocking insulating film formed in the MONOS type memory element.

Next, an alumina film forming apparatus according to another invention includes a processing container in which an object to be processed is placed;
Heating means for heating the object to be processed;
Raw material gas supply means for supplying a raw material gas containing an organoaluminum compound into the processing vessel;
An oxidizing gas supply means for supplying an oxidizing gas comprising water vapor into the processing vessel;
The object to be processed in the processing vessel is heated to a temperature of 200 ° C. or more and 500 ° C. or less, and a film of oxygen-containing aluminum compound containing diaspore is formed on the object to be processed using the source gas and the oxidizing gas. And heating the object on which the oxygen-containing aluminum compound film is formed to a temperature of 800 ° C. or higher and 1,000 ° C. or lower to convert the oxygen-containing aluminum compound film into alumina containing α-alumina. And a step of changing to a film, and a control unit that controls each means to execute the step.

  Furthermore, a storage medium according to another invention is a storage medium used for an alumina film forming apparatus and storing a program that operates on a computer, and the program executes any one of the film forming methods described above. In order to do this, it is characterized by steps.

According to the present invention, the diaspore (α-AlOOH) has a characteristic of changing to α-Al ₂ O ₃ when heated in a relatively low temperature range of about 800 ° C. to 1,000 ° C. First, a film containing a diaspore is formed on the object to be processed using the characteristics, and then the object to be processed is annealed in the temperature range described above, so that α-Al ₂ O can be obtained at a relatively low annealing temperature. _An alumina film containing ₃ can be obtained. For this reason, compared with the method of forming an amorphous alumina film and then heating it at a high temperature of 1,100 ° C. or higher to change it to α-Al ₂ O ₃ , the thermal history given to the object to be processed by annealing is reduced. The effect is small. As a result, for example, this alumina film can be used as a blocking insulating film of a MONOS type memory element, and a band gap with respect to a charge trap layer made of a silicon nitride film or the like under the insulating film is increased to reduce leakage current. A small number of memory elements can be obtained.

Before describing the structure of the film formation apparatus according to this embodiment, the principle of forming an alumina film containing α-Al ₂ O ₃ using the film formation apparatus will be briefly described. As explained in the background art, for example, in order to obtain α-Al ₂ O ₃ from amorphous Al ₂ O ₃ , it is necessary to anneal the formed alumina film at a temperature as high as 1,100 ° C. or higher. The influence of the heat history on the portion already laminated on W (hereinafter referred to as “wafer”) is not preferable. Accordingly, the present inventors searched for a substance that changes to α-Al ₂ O ₃ by annealing in a temperature range of 1,000 ° C. or less that is not affected by such a thermal history. It was found that diaspore (α-AlOOH), which is a kind of the above, is known as a substance that changes to α-Al ₂ O ₃ in a temperature range of 800 ° C. to 1,000 ° C.

Based on such knowledge, the present inventors do not form Al ₂ O ₃ directly on the wafer W, but once form an oxygen-containing aluminum compound film containing diaspore, and then form this film at 800 ° C. It was considered that an alumina film containing α-Al ₂ O ₃ can be obtained at a relatively low temperature by annealing in a temperature range of ˜1,000 ° C. Based on such a concept, the film forming apparatus according to the present embodiment can perform two types of continuous processes, a process of forming a film including a diaspore and a process of executing an annealing process subsequent thereto. It is configured. Here, the oxygen-containing aluminum compound in the present invention includes an aluminum compound containing a so-called hydroxy group (OH group) such as diaspore or boehmite, and further contains an aluminum compound such as amorphous Al ₂ O ₃ as a composition. You may go out.

  Hereinafter, an embodiment in which the present invention is applied to a vertical heat treatment apparatus, which is a batch type heat treatment apparatus, will be described with reference to the longitudinal sectional view of FIG. The film forming apparatus 1 according to the present embodiment switches the raw material gas and the oxidizing gas and alternately supplies them into the reaction vessel, forms one or a few atomic layers or molecular layers by the reaction of both gases, By performing this cycle a plurality of times, these layers are stacked to form a film on the wafer W, and a film forming process is performed by a process called ALD (Atomic Layer Deposition) or MLD (Molecular Layer Deposition). It is configured as. The film forming apparatus 1 also has a function of changing the properties of the film by annealing the wafer W on which the film has been formed by the above-described process.

  In FIG. 2, reference numeral 2 denotes a reaction vessel that forms a processing vessel formed of, for example, quartz in the shape of a vertical cylinder. The lower end of the reaction vessel 2 is opened as a furnace port, A flange 22 is formed integrally with the reaction vessel 2. Below the reaction vessel 2, a lid 23 made of, for example, quartz that contacts the lower surface of the flange 22 and hermetically closes the opening 21 is provided so as to be opened and closed in a vertical direction by a boat elevator (not shown). A cap heater 231 made of, for example, a sheet-like resistance heating element is embedded in the lid body 23 to prevent condensation of water vapor supplied into the reaction vessel 2 as will be described later.

  A rotation shaft 24 is provided through the central portion of the lid body 23, and a wafer boat 25 is mounted on the upper end portion thereof. The wafer boat 25 is provided with three or more, for example, four support columns 26, and a plurality of grooves 26 are provided in the support columns 26 so that a plurality of, for example, 125 wafers W can be held in a shelf shape. (Slot) is formed. However, among the 125 wafer W holding regions, a plurality of dummy wafers are held at both upper and lower ends, and the product wafer W is held in the region between them. A motor M that forms a drive unit that rotates the rotating shaft 24 is provided below the rotating shaft 24, and the motor M can rotate the entire wafer boat 25 via the rotating shaft 24. In addition, a heat retaining unit 27 is provided on the lid 23 so as to surround the rotating shaft 24.

  In the reaction vessel 2, two L-shaped injectors 31, 34, that is, a first gas injector 31 for supplying a processing gas, and a second gas for supplying an oxidizing gas and an inert gas. An injector is inserted through the flange 22 at the bottom of the reaction vessel 2. As shown in FIG. 2, the first gas injector 31 has its tip raised to the upper end of the wafer boat 25, and this raised portion corresponds to each wafer W held on the wafer boat 24. A gas supply hole 311 is provided at the height position.

The first gas injector 31 is connected to the raw material gas supply path 32 on the upstream side. For example, when supplying later-described Al (MMP) ₃ , a valve is provided further upstream of the raw material gas supply path 32. A vaporizer 331 is provided for vaporizing the raw material source via V1. The vaporizer 331 is provided with a raw material source supply source 33 and a carrier gas supply source 332 made of, for example, a nitrogen gas cylinder through mass flow controllers MFC1 and MFC2 and valves V2 and V3. In this case, the raw material in the raw material gas supply source 33 is sent to the vaporizer 331 by, for example, a pressurized gas while being in a liquid state, and reacts with the carrier gas after the vaporizer 331 vaporizes Al (MMP) _3. It is sent into the container 2.

  Here, the raw material gas supply path 32, the vaporizer 331, the raw material source supply source 33, the carrier gas supply source 332, the various valves V1 to V3, and the mass flow controllers MFC1 and MFC2 constitute the raw material gas supply means 3a. Further, for example, when supplying TMA described later, instead of the vaporizer 331 and the carrier gas supply source 332 shown in FIG. 2, a tank or the like storing a raw material is used as the raw material source supply source 33, and this tank is used as a heater or the like. The raw material gas supply means 3a may be configured so that TMA is vaporized by being heated and supplied to the reaction vessel 2.

The raw material source supply source 33 of the film forming apparatus 1 according to the present embodiment includes, for example, TMA (Trimethyl aluminum) represented by the following chemical formula (Chemical Formula 1) and tris (1-methoxy-2- A raw material source containing an organoaluminum compound such as methyl-2-propoxy) aluminum (Tris (1-methoxy-2-methyl-2-propoxy) Aluminum; referred to as Al (MMP) ₃ ) is stored.

なお、以下の説明では原料ガスとしてＴＭＡを用いる場合について説明する。

In the following description, a case where TMA is used as the source gas will be described.

  On the other hand, the second gas injector 34 has substantially the same configuration as the first gas injector 31 described above, and is raised to the upper end portion of the wafer boat 25, and a large number of gases are included in this raised portion. A supply hole 341 is provided so that gas can be supplied to the height position of each wafer W held by the wafer boat 25.

  The second gas injector 34 branches into two on the upstream side, and is connected to an oxidizing gas supply path 35 and an inert gas supply path 39, respectively. A steam generator 36 is connected to the upstream side of the oxidizing gas supply path 35 via a valve V4. Further, the water vapor generator 36 is provided with a hydrogen gas supply source 37 and an oxygen gas supply source 38 via mass flow controllers MFC4 and MFC5 and valves V7 and V8, respectively. 36.

  Here, the steam generator 36 is provided with a heating means for heating the gas passing through the inside, and a catalyst such as platinum is provided in the gas flow path, and oxygen gas and hydrogen gas are supplied at a predetermined temperature of, for example, 500 ° C. or less. The water vapor is generated by contacting the catalyst while heating. For example, the water vapor generator 36 can change the concentration of water vapor supplied into the pressure-reduced reaction vessel 2 in the range of 1% by volume to 90% by volume with respect to the water vapor and oxygen gas. In addition, when supplying water vapor, it goes without saying that a vaporizer that vaporizes water to obtain water vapor may be used instead of supplying water vapor using such a catalyst.

  In addition, for example, nitrogen gas which is an inert gas is supplied to the upstream side of the above-described inert gas supply path 39 branched from the second injector 34 via a mass flow controller MFC3 provided with valves V5 and V6 at the front and rear. A nitrogen gas supply source 30 stored in a cylinder or the like is provided. The various gas supply paths 35 and 39, the valves V6 to V8, the gas supply sources 37, 38, and 30 and the water vapor generator 36 described above constitute a gas supply unit 3b. Of these, various devices (steam generator 36, mass flow controllers MFC4, MFC5, valves V4, V7, V8, hydrogen gas supply source 37, oxygen gas supply source 38) upstream of the oxidizing gas supply path 35 correspond to the oxidizing gas supply means. .

  An exhaust port 4 for exhausting the inside of the reaction vessel 2 is formed above the reaction vessel 2. Connected to the exhaust port 4 is an exhaust pipe 43 having a vacuum pump 41 and pressure adjusting means 42 that can evacuate the reaction vessel 2 to a desired degree of vacuum. Around the reaction vessel 2, a heating furnace 45 provided with a heater 44 as a heating means for heating the inside of the reaction vessel 2 is provided. As the heater 44, it is preferable to use a carbon wire or the like that has no contamination and has excellent temperature rise and fall characteristics.

  Further, the film forming apparatus 1 includes a control unit 5 that controls operations of the heater 44, the pressure adjusting unit 42, and the gas supply unit 3 described above. The control unit 5 includes, for example, a computer including a CPU and a program (not shown). The program includes operations necessary for performing film formation on the wafer W and annealing processing by the film formation apparatus 1, for example, temperature control of the heater 44. In addition, a step (command) group is set for control related to pressure adjustment in the reaction vessel 2 and supply gas flow rate adjustment to the reaction vessel 2. This program is stored in a storage medium such as a hard disk, a compact disk, a magnetic optical disk, or a memory card, and installed in the computer therefrom.

  Next, an example of a film forming method performed using the film forming apparatus 1 will be described with reference to the sequence diagram shown in FIG. In the sequence diagram, FIG. 3 (a) shows the temperature in the reaction vessel 2, FIG. 3 (b) shows the supply timing of TMA to the reaction vessel 2, FIG. 3 (c) shows the supply timing of water vapor, and FIG. ) Indicates the supply timing of nitrogen gas.

  First, a source electrode 101 and a drain electrode 102 are formed on a wafer W that is an object to be processed, for example, a P-type silicon substrate 110 as shown in FIG. 4A, and a silicon oxide film 103a to be a tunnel oxide film 103 is formed thereon. Alternatively, a reaction in which a predetermined number of wafers W on which the silicon nitride film 104a to be the charge trap layer 104 is stacked is held in the wafer boat 25 and then maintained at a temperature of about 150 ° C., for example, as shown in FIG. The wafer boat 25 is loaded into the container 2 by raising a boat elevator (not shown) (loading step).

Subsequently, when the lower end opening 21 of the reaction vessel 2 is blocked by the lid 23, as shown in FIG. 3A, the temperature in the reaction vessel 2 is increased, for example, at a rate of temperature increase of, for example, 50 ° C./min. ° C. or higher, the temperature is raised to for example 300 ° C. temperature range below 500 ℃, e.g. 13.3Pa by vacuum pump 41 and the reaction vessel 2 through the exhaust port ^{4 (0.1torr) ~1.3 × 10 3} Pa ( For example, the exhaust is performed so that the pressure is about 133 Pa (1 Torr) within a range of 10 torr) or less. At this time, the lid body 23 is heated by the already-described cap heater 231 so that the temperature of the lid body 23 surface in the reaction vessel 2 becomes, for example, 150 ° C. Prevent water vapor condensation.

  When the temperature rise and evacuation in the reaction vessel 2 are completed, the process proceeds to a step of forming a film on the wafer W while continuing the operation of the vacuum pump 41. First, as shown in FIG. 3B, TMA is supplied into the reaction vessel 2 for 30 seconds, for example, at a flow rate of, for example, 100 sccm in the range of 50 sccm to 1,000 sccm. At this time, the temperature of the TMA is raised while rising in the first gas injector, and from each gas supply hole 311 to the wafer W at a height position corresponding to each wafer W held in a shelf shape on the wafer boat 25. It is discharged toward.

  The TMA discharged from the gas supply hole 311 is heated in the processing atmosphere in the reaction vessel 2 and adsorbed on the surface of the wafer W while being decomposed. At this time, since TMA is discharged across the surface of each wafer W held in a shelf shape, even if the decomposition speed in the reaction vessel 2 is fast, it is not biased toward the edge portion of the wafer W and is uniform on the wafer surface. Can be adsorbed on.

  Next, when the supply of TMA is stopped, since the evacuation by the vacuum pump 41 is continued, excess TMA that has not been adsorbed on the wafer W is evacuated from the reaction vessel 2. Thereafter, the gas to be supplied is switched to nitrogen gas as shown in FIG. 3D, and further purging of the TMA remaining in the reaction vessel 2 is performed, and then the reaction vessel 2 as shown in FIG. For example, 100 sccm of water in the range of 20 to 500 sccm is supplied for 30 seconds, for example. After stopping the supply of water vapor and evacuating excess water vapor, the gas supplied into the reaction vessel 2 is switched again to nitrogen gas as shown in FIG. Do.

When the combination of the six steps of TMA supply to the reaction vessel 2 → evacuation → nitrogen gas purge → steam supply → evacuation → nitrogen gas purge is one cycle, these steps are performed for 30 cycles, for example, on the wafer W. Film formation is performed (film formation process). Here, when Al (MMP) ₃ is used as the source gas instead of TMA, the supply amount of Al (MMP) ₃ is, for example, in the range of 0.1 sccm to 1.0 sccm on a liquid basis before entering the vaporizer. It is good to adjust so that it may be supplied. Further, the purge with nitrogen gas is not limited to the case where evacuation is performed after the supply of TMA or water vapor. For example, the nitrogen gas purge may be performed immediately after the supply of these gases is stopped.

By alternately supplying TMA and water vapor in this manner, on the surface of the wafer W, TMA (or a decomposition reaction product thereof) adsorbed on the surface of the wafer W is oxidized by water vapor as an oxidizing gas, After being decomposed, an oxygen-containing aluminum compound film 105a including, for example, amorphous Al ₂ O ₃ is formed. Further, since water vapor contains a hydroxy group (OH group) (that is, contains a hydrogen atom and an oxygen atom), an oxygen atom or a hydrogen atom can be incorporated into the oxygen-containing aluminum compound. Due to the interaction between the source gas and the oxidizing gas, the oxygen-containing aluminum compounds include those having a structure close to diaspore (α-AlOOH) and boehmite (γ-AlOOH) containing hydrogen and oxygen. The inventors have found that this is the case. For example, the diaspore and boehmite may be generated based on the reactions shown in the following formulas (1) and (2).
Al (CH ₃ ) ₃ + H ₂ O → AlO (CH ₃ ) + 2CH ₄ (1)
AlO (CH ₃ ) + H ₂ O → AlOOH + CH ₄ (2)

  As described above, various oxygen-containing aluminum compounds are formed on the surface of the wafer W. As described above, the TMA is applied to each wafer W from the first gas injector 31 raised up to the upper end of the wafer boat 25. Supplied and uniformly adsorbed on the surface of the wafer W. Further, with respect to water vapor that reacts with TMA, as with the first gas injector 31, the water vapor is directly applied to each wafer W from each gas supply hole 341 of the second gas injector raised to the upper end of the wafer boat 25. Since it is supplied, for example, compared with the case where water vapor is supplied from the bottom of the reaction vessel 2, TMA and water vapor can be reacted under a uniform temperature condition between the wafer W surfaces.

  As a result, the oxygen-containing aluminum compound film formed by reaction with water vapor has a uniform film thickness and a uniform film quality (composition ratio of the oxygen-containing aluminum compound, etc.) in the plane, and a plurality of wafers. A good quality film with little variation in film thickness and film quality between the W planes can be obtained.

After forming the oxygen-containing aluminum compound film 105a containing the diaspore as shown in FIG. 4B by the above process, the annealing process for changing the diaspore contained in the film 105a to α-Al ₂ O ₃ next. Move on. In the annealing step, nitrogen gas is continuously supplied to the reaction vessel 2 as shown in FIG. 3D, and the pressure in the vessel 2 is set at, for example, 1.3 × 10 ³ Pa (10 torr) to 1.01. For example, it is set to 1.3 × 10 ⁴ Pa (100 torr) within the range of × 10 ⁵ Pa (atmospheric pressure). Further, as shown in FIG. 3 (a), the temperature in the reaction vessel 2 is increased at a rate of temperature increase of, for example, 200 ° C./min. The wafer W in the reaction vessel 2 is annealed.

As described above, in the temperature range of 800 ° C. or more and 1,000 ° C. or less, the diaspore contained in the oxygen-containing aluminum compound film 105a formed on the wafer W becomes α-Al ₂ O ₃ . And change. As a result, an alumina film 105b containing α-Al ₂ O ₃ is formed on the wafer W placed in the reaction vessel 2 as shown in FIG. 4C. The wafer boat 25 is rotated by the motor M during the film forming process and the annealing process described above.

In the annealing process described above, the processing temperature in the range of 800 ° C. to 1,000 ° C. is applied to the laminated structure of the lower layer of the alumina film 105b (the P-type silicon substrate 110 on which the electrodes 101 and 102 are formed, the silicon oxide film 103a, silicon nitride) The influence of thermal history on the membrane 104a) is relatively small. Further, since α-Al ₂ O ₃ is contained in the alumina film 105b changed from the oxygen-containing aluminum compound by annealing, for example, silicon as compared with an alumina film composed entirely of γ-Al ₂ O ₃ is used. Since the average band gap of the entire alumina film 105b with respect to the nitride film 104a is increased, the leakage current can be reduced.

  Returning to the description of the operation of the film forming apparatus 1, when the alumina film 105b is formed on the silicon nitride film 104a by the above-described steps, the supply of the nitrogen gas into the reaction container 2 is continued and the inside of the reaction container 2 is continued. Return pressure to atmospheric pressure. Next, as shown in FIG. 3A, the temperature in the reaction vessel 2 is lowered to, for example, 200 ° C., and the wafer boat 25 is unloaded from the reaction vessel 2 (unloading step). The series of steps described above is performed by controlling the heater 44, the pressure adjusting means 42, the gas supply unit 3, and the like based on the process recipe stored in the control unit 5.

  Thereafter, as shown in FIG. 5, a polysilicon film 106a to be a control gate 106 is formed on the alumina film 105b on the wafer W unloaded from the reaction vessel 2. Thereafter, the gate structure of the tunnel oxide film 103 to the control gate 106 is obtained from these laminated structures by photolithography or the like, and signal lines are connected to the electrodes 101 and 102 and the control gate 106 to obtain the structure shown in FIG. A flash memory device 100 having the structure shown is formed.

The film forming apparatus 1 according to the embodiment described above has the following effects. Since the diaspore (α-AlOOH) has a characteristic of changing to α-Al ₂ O ₃ when heated in a relatively low temperature range of about 800 ° C. to 1,000 ° C., the diaspore is placed on the wafer W. An alumina film 105b containing α-Al ₂ O ₃ can be obtained at a relatively low annealing temperature by annealing the object to be processed in the above-described temperature range after forming the film 105a containing the film. For this reason, compared with the method of forming an amorphous alumina film and then heating it at a high temperature of 1,100 ° C. or higher to change it to α-Al ₂ O ₃ , the thermal history given to the object to be processed by annealing is reduced. The effect is small. As a result, for example, the alumina film 105b can be used as the blocking insulating film 105 of the MONOS type memory element 100, and the band gap with respect to the charge trap layer 104 made of a silicon nitride film or the like under the insulating film 105 is increased. Thus, a memory element with little leakage current can be obtained.

  In the film forming apparatus 1 shown in the embodiment, the case where the film forming process is performed by the ALD process in which the source gas and the oxidizing gas are alternately supplied into the reaction vessel 2 has been described. The oxygen-containing aluminum compound film 105a may be formed by a normal CVD (Chemical Vapor Deposition) process in which an oxidizing gas is continuously supplied simultaneously. Further, in the present embodiment, the case where the film forming step and the subsequent annealing step are performed in the same reaction vessel 2 has been described. However, these steps are configured to be performed in separate apparatuses. Also good.

Furthermore, the type of oxidizing gas used to obtain the oxygen-containing aluminum compound containing diaspore is not limited to water vapor, and for example, hydrogen peroxide gas (H ₂ O ₂ ) is used as a gas containing a hydroxy group. Alternatively, carbon dioxide may be used as the gas containing oxygen atoms, and hydrogen gas may be used as the gas containing hydrogen atoms to supply these two kinds of gases. In addition, the atmosphere in which the annealing process is performed is not limited to the case where the nitrogen gas shown in the embodiment is used, and the annealing process may be performed in an inert gas atmosphere such as argon gas. In addition to the inert gas, for example, annealing may be performed while supplying oxygen gas, or annealing may be performed by performing only vacuum evacuation without supplying gas.

  In addition, the alumina film 105a formed by the film forming apparatus 1 according to the present embodiment is not limited to the case where it is used as the blocking insulating film 105 of the MONOS type flash memory shown in the embodiment. For example, the alumina film 105 formed by the film forming apparatus 1 according to this embodiment can be applied to the insulating film of a DRAM capacitor.

It is sectional drawing which shows the structure of the MONOS type | mold memory element in which the alumina film | membrane of this invention is used. 1 is a longitudinal sectional view showing a film forming apparatus for performing a film forming method of the present invention. It is a sequence diagram which shows the effect | action of the said film-forming apparatus. FIG. 6 is a longitudinal sectional view showing a manufacturing process of the MONOS type memory device. It is a 2nd longitudinal cross-sectional view which shows the said manufacture process.

Explanation of symbols

MFC1 to MFC5
Mass flow controllers V1 to V8 Valve W Wafer 1 Film forming apparatus 2 Reaction vessel 3a Raw material gas supply means 3b Gas supply unit 4 Exhaust port 5 Control unit 21 Opening portion 22 Flange 23 Lid 24 Rotating shaft 25 Wafer boat 26 Column 27 Heat insulation unit 30 Nitrogen gas supply source 31 First gas injector 32 Raw material gas supply path 33 Raw material source supply source 34 Second gas injector 35 Oxidation gas supply path 36 Steam generator 37 Hydrogen gas supply source 38 Oxygen gas supply source 39 Inert gas supply Passage 41 vacuum pump 42 pressure adjusting means 43 exhaust pipe 44 heater 45 heating furnace 100 memory element 101 source electrode 102 drain electrode 103 tunnel oxide film 103a silicon oxide film 104 charge trap layer 104a silicon nitride film 105 blocking insulating film 105a oxygen-containing aluminum Beam compound film 105b alumina film 106 a control gate 106a polysilicon film 110 a silicon substrate 231 cap heater 331 carburetor 311,341
Gas supply hole

Claims (8)

Placing the object to be processed in the processing container;
Introducing a raw material gas containing an organoaluminum compound into the processing vessel;
Introducing an oxidizing gas containing hydrogen atoms and oxygen atoms into the processing vessel;
By heating the processing atmosphere in the processing container in a temperature range of 200 ° C. or higher and 500 ° C. or lower, the raw material gas and the oxidizing gas are reacted to form an oxygen-containing aluminum compound containing diaspore on the surface of the object to be processed. Forming a film;
The object on which the oxygen-containing aluminum compound film is formed is heated in a temperature range of 800 ° C. or more and 1,000 ° C. or less, and the oxygen-containing aluminum compound film is converted into an alumina film containing α-alumina. A method of forming an alumina film, the method comprising:   The film forming method according to claim 1, wherein the step of introducing the source gas into the processing container and the step of introducing the oxidizing gas into the processing container are alternately performed.   3. The film forming method according to claim 1, wherein the organoaluminum compound includes trimethylaluminum or tris (1-methoxy-2-methyl-2-propoxy) aluminum.   4. The film forming method according to claim 1, wherein the oxidizing gas containing hydrogen atoms and oxygen atoms contains a hydroxy group.   The film forming method according to claim 4, wherein the oxidizing gas containing a hydroxy group is water vapor.   6. The method for forming an alumina film according to claim 1, wherein the alumina film is a blocking insulating film formed in a MONOS type memory element. A processing container in which an object to be processed is placed;
Heating means for heating the object to be processed;
Raw material gas supply means for supplying a raw material gas containing an organoaluminum compound into the processing vessel;
An oxidizing gas supply means for supplying an oxidizing gas comprising water vapor into the processing vessel;
The object to be processed in the processing vessel is heated to a temperature of 200 ° C. or more and 500 ° C. or less, and a film of oxygen-containing aluminum compound containing diaspore is formed on the object to be processed using the source gas and the oxidizing gas. And heating the object on which the oxygen-containing aluminum compound film is formed to a temperature of 800 ° C. or higher and 1,000 ° C. or lower to convert the oxygen-containing aluminum compound film into alumina containing α-alumina. A film forming apparatus comprising: a step of changing to a film; and a control unit that controls each means to execute the step. A storage medium used for an alumina film forming apparatus and storing a program operating on a computer,
A storage medium, wherein the program has steps for executing the film forming method according to any one of claims 1 to 6.

Images