JP4905315B2 - Semiconductor manufacturing apparatus, semiconductor manufacturing method, and storage medium - Google Patents

Description

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

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 film 105, and a control gate 106 are stacked on top of each other (the memory element 100 in which the control gate 106 is made 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 film 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 MONOS type memory element 100 described above, a technique using α-Al ₂ O ₃ as the blocking insulating film 105 has been studied. α-Al ₂ O ₃ has a corundum crystal structure and is abundant in minerals, but the band gap is about 8.8 eV larger than that of silicon nitride film and the dielectric constant is high. Therefore, leakage current can be suppressed, and the blocking insulating film 105 can be preferably used. If α-Al ₂ O ₃ is used, the blocking insulating film has a single layer structure. Therefore, there is an advantage that the manufacturing process can be simplified compared to 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 reacting with ozone gas 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 TMA is used to form a film at a temperature higher than 300 ° C., TMA supplied into the processing vessel is thermally decomposed in a gas phase before reaching the center of the semiconductor wafer, and the wall of the processing vessel or the edge of the semiconductor wafer is obtained. It is almost consumed by the adsorption to the semiconductor wafer, and a uniform alumina film cannot be formed on the entire surface 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 1000 ° C. in the actual manufacturing process. However, this alumina film is made of γ-Al ₂ O ₃ , θ-Al ₂ O ₃ , η-Al ₂ O ₃ , spinel, etc. It becomes only Al ₂ O ₃ containing crystals of the structure, and α-Al ₂ O ₃ can hardly be formed. As a result, the band gap with respect to the silicon nitride film becomes as low as about 8.2 eV, and the targeted characteristics cannot be obtained by using α-Al ₂ O ₃ . 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.

Patent Document 2 describes a technique for forming an alumina film on the surface of a cutting tool by reacting aluminum chloride with moisture. In this technique as well, an alumina film containing α-Al ₂ O ₃ is used. The method for forming a film is not described. In particular, when applied to the manufacture of semiconductor elements, it is required to form an alumina film having a uniform thickness on the surface of a semiconductor wafer. Patent Document 2 describes a technique for solving such a problem. In addition, even if α-Al ₂ O ₃ is contained in an alumina film formed by using the present technology, it cannot be applied to the manufacture of a semiconductor device.
JP 2001-234345 A: 0026 paragraph JP-A-10-96081: Paragraph 0004

  The present invention has been made under such circumstances, and its object is to form an alumina film containing α-alumina and having high in-plane uniformity without annealing at a high temperature. A semiconductor manufacturing apparatus, a semiconductor manufacturing method, and a storage medium storing a program for executing the method.

A semiconductor manufacturing apparatus according to the present invention is a semiconductor manufacturing apparatus for forming an alumina film containing α-alumina on a substrate for manufacturing a semiconductor device,
A vertical reaction vessel;
A substrate holder for holding a plurality of substrates in a shelf shape and carrying them into the vertical reaction vessel;
A first gas supply means provided with a gas supply hole for supplying a source gas containing aluminum chloride at a height position corresponding to each substrate held by the substrate holder in the reaction vessel;
A second gas supply means provided with a gas supply hole for supplying an oxidizing gas containing water vapor at a height position corresponding to each substrate held by the substrate holder in the reaction vessel;
Heating means provided so as to surround the reaction vessel;
An exhaust means for exhausting the reaction vessel;
A control unit for heating the processing atmosphere to a temperature within a range of 800 ° C. or more and 1,000 ° C. or less by this heating means, and outputting a control signal for simultaneously supplying and reacting the raw material gas and the oxidizing gas; It is provided with.

  Here, each of the first gas supply unit and the second gas supply unit is configured by a pipe that is raised from the lower part of the reaction vessel to the upper end of the substrate holding unit, and the gas supply hole includes It is preferable that the tube wall portion of the pipe is opened toward the substrate held by the substrate holder. Further, in this semiconductor manufacturing apparatus, the supply amount of aluminum chloride contained in the source gas is in the range of 30 cc / min to 300 cc / min, and the oxidizing gas relative to the supply amount of aluminum chloride contained in the source gas is used. It is suitable when the supply ratio of the water vapor contained is in the range of 1.3 or more and 1.7 or less.

  Further, the alumina film formed in each of the semiconductor manufacturing apparatuses described above is a memory element in which an insulating film made of a high dielectric material, particularly a tunnel oxide film, a charge trap layer, a blocking insulating film, and a control gate are stacked in this order from the bottom. And suitable as the blocking insulating film.

A semiconductor manufacturing method according to another invention is a semiconductor manufacturing method of forming an alumina film containing α-alumina on a substrate for manufacturing a semiconductor device,
A step of holding a plurality of substrates in a shelf shape and carrying these substrates into a vertical reaction vessel;
Heating the treatment atmosphere in the reaction vessel to a temperature of 800 ° C. or higher and 1,000 ° C. or lower;
A first gas supply means having a gas supply hole provided at a height position corresponding to each substrate held by a substrate holder in the reaction vessel while evacuating the reaction vessel, and a second gas supply means Using the gas supply means, a source gas containing aluminum chloride is supplied from the gas supply hole of the first gas supply means, and an oxidizing gas containing water vapor is supplied from the gas supply hole of the second gas supply means. And a step of reacting the source gas and the oxidizing gas to form an alumina film on the surface of each substrate.

  In this semiconductor manufacturing method, the supply amount of aluminum chloride contained in the source gas is in the range of 30 cc / min to 300 cc / min, and the oxidizing gas relative to the supply amount of aluminum chloride contained in the source gas is used. It is preferable that the supply amount ratio of the contained water vapor is in the range of 1.3 or more and 1.7 or less.

  Further, the alumina film manufactured by each of the semiconductor manufacturing methods described above is used as an insulating film made of a high dielectric material, and in particular, a tunnel oxide film, a charge trap layer, a blocking insulating film, and a control gate are laminated in this order from the bottom. In a memory element, it is suitable when used as the blocking insulating film.

  In addition, a storage medium according to the present invention is a storage medium that stores a program that is used in an alumina film forming apparatus and that operates on a computer, and is a step for executing any of the semiconductor manufacturing methods described above. It is characterized by being assembled

According to the present invention, an alumina film containing α-Al ₂ O ₃ is formed by reacting a source gas containing aluminum chloride with an oxidizing gas containing water vapor at a temperature of 800 ° C. to 1,000 ° C. Yes. Further, in the above temperature range, the reaction rate between aluminum chloride and water vapor is extremely high, but the raw material gas and the oxidizing gas are applied to each substrate from the side of the substrate group arranged vertically in the vertical reaction vessel. Are supplied by separate supply means, both gases are separately distributed to the central region of the substrate and react, so that an alumina film with high in-plane uniformity can be obtained.

Before describing the configuration of the semiconductor manufacturing apparatus according to the present embodiment, the gist of the present invention will be briefly described. As described in the background art, an alumina film formed at a relatively low temperature of about 300 ° C. using TMA as a raw material is annealed at a temperature of 1,100 ° C. or higher after the film formation, and amorphous Al ₂ O ₃ was crystallized and phase transitioned to obtain α-Al ₂ O ₃ . Therefore, the present inventors have performed annealing temperatures (1,100) performed on Al ₂ O _{3 having} a spinel structure such as amorphous or γ-Al ₂ O ₃ which is higher than the TMA film forming temperature (300 ° C.). C.) When a substance capable of obtaining α-Al ₂ O ₃ without annealing was formed by forming an alumina film within a lower temperature range, aluminum chloride (AlCl ₃ ) was heated to 800 ° C. It was found that an alumina film containing α-Al ₂ O ₃ can be formed by reacting with an oxidizing gas in a temperature range of ˜1,000 ° C. Based on such knowledge, the semiconductor manufacturing apparatus according to the present embodiment is configured such that an alumina film containing α-Al ₂ O ₃ can be formed without using an annealing process using AlCl ₃ as a source gas. Yes.

Further, when AlCl ₃ is reacted at a relatively high temperature of 800 ° C. to 1,000 ° C., the oxidizing gas to be reacted with AlCl ₃ needs to exhibit activity in this temperature range. In this regard, ozone gas that has been conventionally used as an oxidizing gas for TMA is known to lose its activity in such a temperature range. Therefore, the semiconductor manufacturing apparatus according to the present embodiment is also characterized in that water vapor that does not lose activity even in a relatively high temperature range of 800 ° C. to 1,000 ° C. is used as the oxidizing gas.

  Hereinafter, an embodiment in which the present invention is applied to a vertical heat treatment apparatus which is a batch type semiconductor manufacturing apparatus will be described with reference to a vertical sectional view of FIG. The semiconductor manufacturing apparatus according to the present embodiment (hereinafter referred to as film forming apparatus 1) is applied to wafer W by a CVD (Chemical Vapor Deposition) process in which a source gas and an oxidizing gas are supplied simultaneously and reacted to react both gases. It is comprised as an apparatus which performs film-forming of this.

  In FIG. 2, reference numeral 2 denotes a reaction vessel that is a processing vessel formed of, for example, quartz in a vertical cylindrical shape. The lower end of the reaction vessel 2 is opened as a furnace port, and a flange 22 is formed integrally with the reaction vessel 2 at the periphery of the opening 21. 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 rotation shaft 24 is provided through the central portion of the lid 23, and a wafer boat 25 as a substrate holder is mounted on the upper end portion of the rotation shaft 24.

  The wafer boat 25 is provided with three or more, for example, four support columns 26, and a substrate holding portion is provided on the support columns 26 so that a plurality of, for example, 125 wafers W to be processed can be held in a shelf shape. A large number of grooves (slots) are 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, injectors 31 and 34, which are gas supply means composed of two L-shaped pipes, that is, a first gas injector 31 for supplying a processing gas, an oxidizing gas and an inert gas are supplied. A second gas injector 34 for supply is inserted through the flange 22 below 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 is held by the wafer boat 24 on the pipe wall of the raised portion of the pipe. A gas supply hole 311 is provided at a height position corresponding to each wafer W. Here, the “height position corresponding to each wafer W” is not limited to the case where the height position of each gas supply hole 311 exactly coincides with each wafer W held in the wafer boat 25. For example, the gas supply hole 311 The height position of 311 and the wafer W may be shifted by several millimeters in the vertical direction, and for example, one gas supply hole 311 may be provided for every several wafers W.

The first gas injector 31 is connected to the source gas supply path 32 on the upstream side, and on the further upstream side of the source gas supply path 32, a source source supply source 33 is provided via valves V1 and V2 and a mass flow controller MFC1. Is connected. Inside the raw material source supply source 33, for example, solid and anhydrous aluminum chloride (AlCl ₃₎ is stored, by heating the container of AlCl ₃ by a heating means (not shown) for example, a resistance heating element, AlCl ₃ Is sublimated to obtain AlCl ₃ gas (raw material gas). Here, the raw material gas supply path 32, the raw material source supply source 33, the various valves V1 and V2, and the mass flow controller MFC1 constitute a raw material gas supply unit 3a.

  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, and gas can be supplied to a height position corresponding to each wafer W held by the wafer boat 25. Here, regarding the “height position corresponding to each wafer W”, the height positions of the gas supply hole 341 and the wafer W are several in the vertical direction, as in the case of the gas supply hole 311 of the first gas injector 31. It may be shifted by mm, or one gas supply hole 341 may be provided for every several wafers W.

  As shown in FIG. 2, the second gas injector 34 has a diameter of the wafer W on the wafer boat 25 with respect to the opening direction of each gas supply hole 311 provided in the first gas injector 31 described above. The gas supply holes 341 of the second gas injector 34 are installed in the reaction vessel 2 so as to open at positions facing in the direction.

  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 V5. 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 MFC3 and MFC4 and valves V6 and V7, 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 MFC2 provided with valves V3 and V4 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 V3 to V7, the gas supply sources 37, 38, and 30 and the water vapor generator 36 described above constitute a gas supply unit 3b.

  Further, 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. These vacuum pump 41 and pressure adjusting means 42 constitute exhaust means. 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 units 3a and 3b described above. The control unit 5 includes a computer having a CPU and a program (not shown), for example. The program includes operations necessary for performing film forming processing on the wafer W by the film forming apparatus 1, for example, temperature control and reaction of the heater 44. A group of steps (commands) for adjusting pressure in the container 2 and controlling the supply amount of the processing gas and the oxidizing gas to the reaction container 2 is assembled. 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 processing temperature in the reaction vessel 2, FIG. 3 (b) shows the supply timing of the raw material gas (AlCl ₃ ) to the reaction vessel 2, and FIG. 3 (c) shows the oxidizing gas ( FIG. 3D shows the supply timing of the purge gas (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).

Subsequently, when the lower end opening 21 of the reaction vessel 2 is closed by the lid 23, as shown in FIG. 3A, the temperature in the reaction vessel 2 is increased at a rate of temperature increase of, for example, 200 ° C./min. The temperature is raised to, for example, 950 ° C. in a temperature range of not less than 1000 ° C. and not more than 1,000 ° C., and the inside of the reaction vessel 2 is passed through the exhaust port 4 by a vacuum pump 41, for example, 13.3 Pa (0.1 torr) to 1.3 × 10 ³ Exhaust is performed so that the pressure is, for example, about 33.3 Pa (0.25 Torr) within a range of Pa (10 torr) or less.

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, AlCl ₃ gas is continuously supplied into the reaction vessel 2 at a flow rate of, for example, 30 sccm in the range of 30 sccm to 300 sccm. At this time, the temperature of the AlCl ₃ gas is raised while rising in the first gas injector 31, and from each gas supply hole 311 at a height position corresponding to each wafer W held in a shelf shape on the wafer boat 25. It is discharged toward the wafer W.

In parallel with the supply of the AlCl ₃ gas from the first gas injector, as shown in FIG. 3C, for example, water vapor having a concentration of 90% by volume is supplied from the second gas injector in the range of 20 to 500 sccm. For example, at a flow rate of 50 sccm. At this time, the temperature of the water vapor is also raised while rising in the second gas injector 34, and the wafer is discharged from each gas supply hole 341 at a height corresponding to each wafer W held in a shelf shape on the wafer boat 25. Discharged toward W.

When the AlCl ₃ gas and the water vapor are continuously supplied into the reaction vessel 2 in this manner, these gases react to form Al ₂ O ₃ based on the reaction formula shown in the following formula (1).
2AlCl ₃ + 3H ₂ O → Al ₂ O ₃ + 6HCl (1)
Here, the atmosphere in the reaction vessel 2 where Al ₂ O ₃ is formed is a temperature atmosphere of 950 ° C. in the range of 800 ° C. to 1,000 ° C. as described above. ₃ high vapor pressure of the gas, when supplied AlCl ₃ gas alone into the reaction vessel 2, AlCl ₃ gas would be discharged from the reaction vessel 2 without substantially adsorbed on the wafer W.

Therefore, in the film forming apparatus 1 according to the present embodiment, as described above, the height corresponding to each wafer W raised to the upper end portion of the wafer boat 25 and held on the wafer boat 25 in a shelf shape is provided. While supplying the AlCl ₃ gas from the gas supply hole 311 provided in the position, water vapor as an oxidizing gas is supplied simultaneously with the supply of the AlCl ₃ gas. By simultaneously supplying AlCl ₃ gas and water vapor in this manner, the reaction shown in the formula (1) proceeds in the vicinity of the surface of the wafer W, and the generated Al ₂ O ₃ is deposited on the surface of the wafer W. An alumina film can be formed on the surface of the wafer W.

Further, since the reaction rate between the AlCl ₃ gas and water vapor shown in the formula (1) has a very high reaction rate, when these gases come into contact with each other, Al ₂ O ₃ is rapidly formed. For this reason, for example, when it is configured to supply AlCl ₃ gas and water vapor from two gas injectors 31 and 34 arranged side by side, these gases supplied from the gas supply holes 311 and 341 are in the vicinity of the injectors 31 and 34. Since the reaction immediately occurs in the vicinity of the wall surface of the reaction vessel 2 and the peripheral edge of the wafer W, an alumina film cannot be formed on the entire surface of the wafer W.

  Therefore, in the film forming apparatus 2 according to the present embodiment, as described above, the gas supply hole 311 of the first injector and the gas supply hole 341 of the second gas injector 34 have the diameter of the wafer W on the wafer boat 25. It is provided so as to face the direction. Therefore, each gas supplied from the gas supply holes 311 and 341 can be contacted while being diffused in the radial direction of the wafer W, so that a uniform alumina film can be formed in the radial direction of the wafer W. . Further, since the wafer boat 25 is rotated by the motor M during the film formation period, a uniform alumina film can be formed even in the circumferential direction of the wafer W.

Further, in the film forming apparatus 1 according to the present embodiment, the gas supply holes 311 and 341 are opposed to each other in the diameter direction of the wafer W so that the alumina film having a uniform film thickness is formed. In addition, adjustments are made to form an alumina film having a uniform thickness even under process conditions. That is, in the reaction shown in the formula (1), if the supply amount of either one of AlCl ₃ gas, water vapor, or both is too large, the reaction abruptly proceeds to the right side, and each gas is applied to the surface of the wafer W. Al ₂ O ₃ is formed before it is sufficiently distributed, and an alumina film having a non-uniform film thickness (poor in-plane uniformity) is formed. On the other hand, even if the supply amount ratio of these gases is supplied in a balanced manner so that the alumina film is uniformly formed on the surface of the wafer W, if the supply amount of these gases is too small, the film formation time is long. There is a demerit that it becomes.

Therefore, the film forming apparatus 1 according to the present embodiment, as shown in experimental examples described later, (a) the supply amount of the AlCl ₃ gas is, for example, 30 sccm within the range of 30 sccm to 300 sccm, for example (b) By setting the ratio of the supply amount of water vapor to the supply amount of the AlCl ₃ gas to, for example, 1.7 (50 sccm) within the range of 1.3 to 1.7, for example, it is uniform within the range of realistic film formation time. It is set so that a simple alumina film can be formed.

  In the film forming apparatus 1, film formation is performed at a relatively high temperature of 950 ° C. in the range of 800 ° C. to 1,000 ° C. In such a temperature range, unstable oxidizing gas such as ozone gas is oxidized gas. There is a tendency to lose activity as. On the other hand, in the film forming apparatus 1 according to the present embodiment, water vapor is employed as the oxidizing gas, and since water vapor has a stable oxidizing power even in the above temperature range, TMA is used. The alumina film 105a can be formed at a film formation speed comparable to the conventional method.

By continuously supplying AlCl ₃ gas and water vapor, for example, for 30 minutes under such apparatus conditions and process conditions, an alumina film 105a is formed on the surface of the wafer W as shown in FIG. 4B. . Since the film is formed at a temperature of 950 ° C. in the range of 800 ° C. to 1,000 ° C., which is higher than the film forming temperature of 300 ° C. in the conventional film forming method using TMA, The inventors have found that the alumina film 105a is crystallized, and that the crystallized alumina film 105a contains a relatively large amount of α-Al ₂ O ₃ . As a result, for example, the average band gap of the entire alumina film 105a with respect to the silicon nitride film 104a is higher than that of an alumina film composed entirely of γ-Al ₂ O ₃ , so that leakage current can be reduced. It becomes possible.

  Further, the temperature within the range of 800 ° C. to 1,000 ° C. is the portion laminated on the lower layer side of the alumina film 105a (the P-type silicon substrate 110 on which the electrodes 101 and 102 are formed, the silicon oxide film 103a, the silicon nitride film). The influence of the thermal history on the membrane 104a) can be relatively small.

Returning to the description of the operation of the film forming apparatus 1, when the alumina film 105a is formed on the silicon nitride film 104a by the above-described steps, the reaction container 2 is filled as shown in FIGS. 3 (b) and 3 (c). The supply of AlCl ₃ gas and water vapor to the reactor is stopped, and the pressure in the reaction vessel 2 is returned to atmospheric pressure while supplying purge gas (nitrogen gas) from the inert gas supply passage 39 as shown in FIG. At the same time, after the temperature in the reaction vessel 2 is lowered to, for example, 200 ° C., the supply of the purge gas is stopped and the wafer boat 25 is unloaded from the reaction vessel 2. The series of steps described above is performed by controlling the heater 44, the pressure adjusting unit 42, the gas supply units 3a, 3b, and the like based on the process recipe stored in the control unit 5.

  Thereafter, as shown in FIG. 4C, a polysilicon film 106a to be a control gate 106 is formed on the alumina film 105a 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. The alumina film 105a containing α-Al ₂ O ₃ is formed by reacting the source gas AlCl ₃ gas and the oxidizing gas water vapor at a temperature of 800 ° C. to 1,000 ° C. Further, in the above temperature range, the reaction rate between aluminum chloride and water vapor is extremely high, but from the side of the wafer W group arranged vertically in the reaction vessel 2 of the film forming apparatus 1 to each wafer W. Since the source gas and the oxidizing gas are supplied by the separate gas injectors 31 and 34, both gases reach the central region of the wafer W and react separately, so that an alumina film 105a with high in-plane uniformity is obtained. Can do.

  Note that 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.

(Experiment 1)
Using the film forming apparatus 1 shown in FIG. 2, an AlCl ₃ gas and water vapor were reacted to form an alumina film 105a on the wafer W, and its crystal structure was examined. As a comparative example, the alumina film 105a formed by the conventional method using TMA was annealed, and the crystal structure was examined. The alumina film 105a is formed by the CVD method for continuously supplying the source gas and the oxidizing gas for the following (Example 1), and the source gas and the oxidizing gas are alternately and repeatedly supplied for the (Comparative Example 1). The MLD method was used.

A. Experimental conditions
Example 1
Source gas: AlCl ₃ gas
Oxidizing gas: water vapor
Process temperature: 950 ° C
Process pressure: 33.3 Pa (0.25 Torr)
Raw material gas supply: 30 sccm
Oxidizing gas supply amount: 50 sccm
Deposition time: 30 minutes

(Comparative Example 1)
Deposition conditions
Source gas: TMA gas
Oxidizing gas: Ozone gas
Process temperature: 300 ° C
Process pressure:
TMA gas 40.0 Pa (0.3 Torr)
Ozone gas 133.3 Pa (1.0 Torr)
Source gas supply: 300sccm
Oxidizing gas supply amount: 200 g / Nm ³ (concentration in oxygen gas 10 slm)
Deposition time:
TMA gas 15 seconds / cycle
Ozone gas 20 seconds / cycle
Total 200 cycles
Annealing conditions
Process atmosphere: Nitrogen atmosphere
Process temperature: 1,000 ° C
Process pressure: 1.01 × 10 ⁵ Pa (atmospheric pressure)
Annealing time: 60 minutes

B. Experimental result
FIG. 5 is a graph summarizing the composition ratio of the crystal structure of Al ₂ O ₃ contained in the alumina film 105a obtained in (Example 1) and (Comparative Example 1). The column shown on the left side of the graph shows the composition ratio of the alumina film 105a obtained in (Example 1), and the column shown on the right side shows the composition ratio of (Comparative Example 1). The composition ratio of each alumina film was determined by analyzing image data obtained from a TEM (Transmission Electron Microscope).

According to the results of (Example 1), the alumina film 105a obtained by reacting AlCl ₃ gas and water vapor at a process temperature of 950 ° C. has a θ-phase, α-phase, η-phase, and γ-phase. Four types of crystal structures were included. Among these, α-Al ₂ O ₃ (α phase), which is the target substance of the present embodiment, is the third largest after the θ phase and η phase, and is contained in 18% of the entire alumina film 105a. .

In contrast, the alumina film 105a obtained by combining the film formation using TMA and the subsequent annealing (Comparative Example 1) includes six types of crystal structures including the χ phase and the θ phase. However, the target substance α-Al ₂ O ₃ (α phase) was the smallest among these six types of crystal structures, and contained only 3% of the total.

From these results, when comparing the alumina film 105a obtained in each experiment of (Example 1) and (Comparative Example 1), the film was obtained from (Example 1) formed from AlCl ₃ gas and water vapor. The alumina film 105a contains about 6 times as much α-Al ₂ O ₃ as (Comparative Example 1). As a result, the average band gap of the alumina film 105a formed in (Example 1) is higher than that in (Comparative Example 1), and the alumina film 105a of (Example 1) is used. It can be seen that the leakage current when the MONOS type flash memory is configured can be reduced.

(Experiment 2)
When the film formation apparatus 1 shown in FIG. 2 is used to react the AlCl ₃ gas and water vapor to form the alumina film 105a, the supply amount of the water vapor is changed by fixing the supply amount of the AlCl ₃ gas. The film thickness of the formed alumina film and the uniformity of the film thickness between the central part and the peripheral part of the wafer W were examined.

A. Experimental conditions Raw material gas: AlCl ₃ gas
Oxidizing gas: water vapor
Process temperature: 950 ° C
Process pressure: 33.3 Pa (0.25 Torr)
Raw material gas supply: 30 sccm
Deposition time: 5 minutes
(Example 2)
Oxidizing gas supply (100% volume conversion)
: 40sccm
Supply ratio R (water vapor supply / AlCl ₃ gas supply)
: 1.33
Example 3
Oxidizing gas supply (100% volume conversion)
: 50sccm
Supply ratio R: 1.67
(Comparative Example 2)
Oxidizing gas supply (100% volume conversion)
: 25sccm
Supply ratio R: 0.83
(Comparative Example 3)
Oxidizing gas supply (100% volume conversion)
: 75sccm
Supply amount ratio R: 2.50

B. Experimental result
FIG. 6 shows the result of plotting the film thickness in a predetermined region on the wafer W of the alumina film 105a obtained in each Example and Comparative Example in (Experiment 2). In the figure, the horizontal axis indicates the amount of water vapor supplied during film formation, and the vertical axis indicates the film thickness of the formed alumina film 105a. The black circle “●” plot represents the average value of the film thickness at the 24 measurement points on the peripheral edge of the wafer W of the alumina film 105a obtained in these examples and comparative examples. "Is the average film thickness of 25 measurement points in the center of the wafer W. A black diamond “♦” plot represents the average film thickness of 49 measurement points of the entire wafer W. In addition, the enclosure of a broken line has shown that it is a measurement result obtained by the same Example and the comparative example.

According to FIG. 6, the film thickness at the peripheral portion of the wafer W tends to be thicker than the film thickness at the central portion in both (Examples 2 and 3) and (Comparative Examples 2 and 3). As shown in FIG. 2, since the gas injectors 31 and 34 supply Al ₂ O ₃ gas and water vapor to the peripheral portion of the wafer W, film formation proceeds first in the vicinity of the gas supply unit. However, it is considered that the film thickness has increased compared to the central portion of the wafer W far from the supply portion.

However, in (Example 2) (supply ratio R = 1.33) and (Example 3) (R = 1.67), the difference in film thickness between the wafer W peripheral portion and the central portion is about 5 nm. On the other hand, in the case where the supply amount of water vapor is the largest (Comparative Example 2) (R = 2.50), this film thickness difference spreads by about 4 times to about 20 nm. This is because when the excess water vapor is supplied in the vicinity of the gas injector 34 to which water vapor is supplied, the reaction of the formula (1) rapidly proceeds at the periphery of the wafer W near the injector 34 while the center of the wafer W is centered. It is thought that this is because even the AlCl ₃ gas to be distributed to the part has been consumed at the peripheral part. This means that when the film thickness of the entire wafer W is compared between (Example 3) and (Comparative Example 3), there is no significant difference, and the total amount of alumina formed on the wafer W is It can be explained from the fact that there is no big difference.

On the other hand, in the case where the supply amount of water vapor is small (Comparative Example 1) (R = 0.83), there is no significant difference in film thickness between the peripheral portion and the central portion of the wafer W as in (Comparative Example 3). However, the film thickness of the entire wafer W is less than half that of the second embodiment, and the film formation rate is slow. This is thought to be because the amount of water vapor supplied is too small relative to the amount of AlCl ₃ gas supplied, so that the reaction of formula (1) does not easily proceed to the right. From the above, in order to make the film formation rate not too slow and to improve the in-plane uniformity of the film thickness, when the supply amount of AlCl ₃ gas is set to 30 sccm within the range of 30 sccm to 50 sccm, for example, It can be said that it is appropriate to adjust the ratio of the supply amount of water vapor to the supply amount of the AlCl ₃ gas within a range of 1.3 to 1.7, for example.

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 characteristic view which shows the composition ratio of the crystal structure of the alumina film | membrane formed into a film using different source gas. It is a characteristic view which shows the change of the film thickness of the alumina film formed into a film by changing the process conditions of the said film-forming apparatus.

Explanation of symbols

MFC1 to MFC4
Mass flow controllers V1 to V7 Valve W Wafer 1 Film forming apparatus 2 Reaction vessel 3a Raw material gas supply unit 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 alumina film 106 Control gate 106a Polysilicon film 110 Silicon substrates 311 and 341
Gas supply hole

Claims (12)

A semiconductor manufacturing apparatus for forming an alumina film containing α-alumina on a substrate for manufacturing a semiconductor device,
A vertical reaction vessel;
A substrate holder for holding a plurality of substrates in a shelf shape and carrying them into the vertical reaction vessel;
A first gas supply means provided with a gas supply hole for supplying a source gas containing aluminum chloride at a height position corresponding to each substrate held by the substrate holder in the reaction vessel;
A second gas supply means provided with a gas supply hole for supplying an oxidizing gas containing water vapor at a height position corresponding to each substrate held by the substrate holder in the reaction vessel;
Heating means provided so as to surround the reaction vessel;
An exhaust means for exhausting the reaction vessel;
A control unit for heating the processing atmosphere to a temperature within a range of 800 ° C. or more and 1,000 ° C. or less by this heating means, and outputting a control signal for simultaneously supplying and reacting the raw material gas and the oxidizing gas; A semiconductor manufacturing apparatus comprising:   Each of the first gas supply means and the second gas supply means is configured by a pipe that starts up from the lower part of the reaction vessel to the upper end of the substrate holding part, and the gas supply hole is formed of the pipe. The semiconductor manufacturing apparatus according to claim 1, wherein an opening is formed in a tube wall portion toward a substrate held by the substrate holder.   3. The semiconductor manufacturing apparatus according to claim 1, wherein the supply amount of aluminum chloride contained in the source gas is in a range of 30 cc / min to 300 cc / min.   4. The semiconductor according to claim 3, wherein a ratio of a supply amount of water vapor contained in the oxidizing gas to a supply amount of aluminum chloride contained in the source gas is in a range of 1.3 or more and 1.7 or less. Manufacturing equipment.   5. The semiconductor manufacturing apparatus according to claim 1, wherein the alumina film is used as an insulating film made of a high dielectric material.   6. The semiconductor according to claim 5, wherein the alumina film is used as the blocking insulating film in a memory element in which a tunnel oxide film, a charge trap layer, a blocking insulating film, and a control gate are stacked in this order from the bottom. Manufacturing equipment. A semiconductor manufacturing method for forming an alumina film containing α-alumina on a substrate for manufacturing a semiconductor device,
A step of holding a plurality of substrates in a shelf shape and carrying these substrates into a vertical reaction vessel;
Heating the treatment atmosphere in the reaction vessel to a temperature of 800 ° C. or higher and 1,000 ° C. or lower;
A first gas supply means having a gas supply hole provided at a height position corresponding to each substrate held by a substrate holder in the reaction vessel while evacuating the reaction vessel, and a second gas supply means Using the gas supply means, a source gas containing aluminum chloride is supplied from the gas supply hole of the first gas supply means, and an oxidizing gas containing water vapor is supplied from the gas supply hole of the second gas supply means. And a step of reacting these source gas and oxidizing gas to form an alumina film on the surface of each substrate.   The semiconductor manufacturing method according to claim 7, wherein a supply amount of aluminum chloride contained in the source gas is in a range of 30 cc / min to 300 cc / min.   9. The semiconductor according to claim 8, wherein a ratio of a supply amount of water vapor contained in the oxidizing gas to a supply amount of aluminum chloride contained in the source gas is in a range of 1.3 or more and 1.7 or less. Production method.   10. The semiconductor manufacturing method according to claim 7, wherein the alumina film is used as an insulating film made of a high dielectric material.   11. The semiconductor according to claim 10, wherein the alumina film is used as the blocking insulating film in a memory element in which a tunnel oxide film, a charge trap layer, a blocking insulating film, and a control gate are stacked in this order from the bottom. Production method. A storage medium used for an alumina film forming apparatus and storing a program operating on a computer,
A storage medium comprising steps for executing the semiconductor manufacturing method according to any one of claims 7 to 11.

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