JP2015191955A - Film formation method, film formation apparatus and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a thin film of good film quality in forming a thin film by supplying material gas and ozone gas to substrates stacked to a ledge in a reaction tube in order.SOLUTION: A film formation method by alternately supplying an organic zirconium gas and a reactive gas including an ozone gas to a wafer W to form a zirconium oxide film comprises: an atmosphere replacement step of replacing an inside atmosphere in a reaction tube 12 at the time of switching between the organic zirconium gas and the reactive gas. The film formation method further comprises the steps of: plotting the correlation between a time t of the atmosphere replacement step performed after the supply of the reactive gas, and a film growth amount D of the zirconium oxide film; calculating a decline rate of the film growth amount D per 80 seconds; and setting the time t so that the decline rate becomes less than 1.5%.

Description

  The present invention relates to a film forming method, a film forming apparatus, and a film forming method for forming a thin film by sequentially supplying processing gases that react with each other to substrates held in a shelf shape on a substrate holder in a reaction tube. The present invention relates to a stored storage medium.

As a method for forming a high dielectric constant film (eg, zirconium oxide (Zr—O) film) on a substrate such as a semiconductor wafer (hereinafter referred to as “wafer”), processing gases that react with each other are alternately supplied to the wafer. An ALD (Atomic Layer Deposition) method is known in which reaction products of these processing gases are stacked. As an example of the processing gas, an organic zirconium gas (tris (dimethylamino) cyclopentadienyl / zirconium gas) which is a raw material gas and an ozone (O ₃ ) gas which is an oxidizing gas are used.

As an apparatus for forming such a high dielectric constant film, there is a batch type vertical heat treatment apparatus that performs film formation processing on a large number of wafers at once. In this apparatus, a wafer boat (substrate holder) on which wafers are loaded in a shelf shape is airtightly transferred from below into a vertical reaction tube, and the gas nozzles provided in the reaction tube along the wafer boat are described above. The film forming process is performed by alternately supplying the process gas. When these processing gases are switched, an atmosphere replacement process including evacuation of the reaction tube and purging of nitrogen (N ₂ ) gas is performed.

By the way, the high dielectric constant film is required to have a leakage current as small as possible, and the relative dielectric constant (k value) is also required to be as high as possible. Therefore, it is necessary to reduce the impurity concentration remaining in the high dielectric constant film as much as possible. Japanese Patent Laid-Open No. 2004-228561 discloses a nitrogen gas supply process performed after supplying DCS gas when forming a silicon nitride film by ALD using DCS (dichlorosilane) gas and ammonia (NH ₃ ) gas. It describes a technology that can save seconds. However, Patent Document 1 does not describe a process using ozone gas.

Patent No. 5208294

  The present invention has been made in view of such circumstances, and its purpose is to form a thin film by sequentially supplying a source gas and an ozone gas to a substrate stacked in a shelf shape in a reaction tube. An object of the present invention is to provide a technique capable of obtaining a thin film having good film quality.

The film forming method of the present invention comprises:
A film forming cycle for sequentially supplying a reaction gas containing an organic source gas and ozone gas to a plurality of substrates held in a shelf shape on a substrate holder in a reaction tube is repeated a plurality of times, and the organic source gas and In a film forming method of laminating a reaction product with ozone gas on a substrate,
The film formation cycle includes an atmosphere including a pre-stage for evacuating the inside of the reaction tube and a post-stage for supplying an inert gas after the supply of the reaction gas is stopped and before the supply of the organic source gas is started. Including a replacement step,
The film formation amount obtained by carrying out the film formation cycle by setting the previous step and the subsequent step of the atmosphere replacement process one time each at the same time is defined as D, and the total amount to be applied to the previous step and the subsequent step In the graph showing the relationship between the time t and the film formation amount D, the film formation amount D decreases as the time t increases, and when the time t increases 80 seconds, the decrease rate of the film formation amount D is 1.5% or less. If the film-forming amount D becomes D0,
The atmosphere replacement step is performed such that a film formation amount D when the film formation cycle is performed is D0.

The film forming apparatus of the present invention
A film forming cycle for sequentially supplying a reaction gas containing an organic source gas and ozone gas to a plurality of substrates held in a shelf shape on a substrate holder in a reaction tube is repeated a plurality of times, and the organic source gas and In a film forming apparatus for laminating a reaction product with ozone gas on a substrate,
After the supply of the reaction gas is stopped and before the supply of the organic material gas is started, an atmosphere replacement process including a pre-step for evacuating the inside of the reaction tube and a post-step for supplying an inert gas is then formed. A control unit that outputs a control signal to perform as part of the cycle,
The film formation amount obtained by carrying out the film formation cycle by setting the previous step and the subsequent step of the atmosphere replacement process one time each at the same time is defined as D, and the total amount to be applied to the previous step and the subsequent step In the graph showing the relationship between the time t and the film formation amount D, the film formation amount D decreases as the time t increases, and when the time t increases 80 seconds, the decrease rate of the film formation amount D is 1.5% or less. If the film-forming amount D becomes D0,
The control unit outputs a control signal so as to perform the atmosphere replacement step so that a film formation amount D when the film formation cycle is performed becomes D0.
The storage medium of the present invention is
A storage medium storing a computer program that runs on a computer,
The computer program is characterized in that steps are set so as to implement the above-described film forming method.

  In the present invention, for a film formation amount (film thickness dimension) D of a reaction product obtained by a reaction between an organic source gas and ozone gas, supply of the organic source gas is started after supplying a reaction gas containing ozone gas. The time t is set within a certain range, paying attention to the fact that the longer the time t spent in the atmosphere replacement step performed earlier, the smaller the time t is set. Specifically, the time t is when the film formation cycle is performed, assuming that the film formation amount D is such that the decrease rate of the film formation amount D is 1.5% or less when the time t increases by 80 seconds. The film formation amount D is set to D0. For this reason, the reaction product is less likely to incorporate the organic substance in the organic source gas, so that a thin film having good film quality can be obtained.

It is a longitudinal cross-sectional view which shows an example of the film-forming apparatus of this invention. It is a cross-sectional top view which shows the said film-forming apparatus. It is a flowchart which shows the film-forming method of this invention. It is the schematic which shows an example of the film-forming method of this invention. It is the schematic which shows an example of the film-forming method of this invention. It is the schematic which shows an example of the film-forming method of this invention. It is the schematic which shows an example of the film-forming method of this invention. It is a schematic diagram which shows typically the characteristic acquired by this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention. It is a characteristic view which shows the characteristic acquired in the Example of this invention.

  Regarding an example of an embodiment according to the film forming method of the present invention, a film forming apparatus for performing this film forming method will be briefly described first. As shown in FIGS. 1 and 2, the film forming apparatus includes a wafer boat 11 on which a large number of, for example, 150 wafers W are stacked in a shelf shape, and the wafer boat 11 is stored in an airtight manner to the wafers W. And a reaction tube 12 that collectively performs the film forming process. A substantially cylindrical heating furnace main body 14 having an opening on the lower surface side is provided outside the reaction tube 12, and a heater 13 as a heating mechanism is disposed on the inner wall surface of the heating furnace main body 14 in the circumferential direction. ing.

  As shown in FIG. 1 and FIG. 2, the reaction tube 12 has a double tube structure of an outer tube 12a and an inner tube 12b housed in the outer tube 12a, and is a generally cylindrical shape whose upper and lower surfaces are open. The shape flange portion 18 is airtightly supported from the lower side. As shown in FIG. 2, the portion on one end side (front side) of the inner tube 12b when viewed in a plane is formed so as to swell toward the outer tube 12a over the length direction of the inner tube 12b. The region 12c for accommodating the gas nozzles 51a to 51c is formed. As shown in FIG. 2, the portion of the inner tube 12b that faces the region 12c is opened over the length of the inner tube 12b, forming a slit 17 that is an exhaust port.

In this example, as shown in FIG. 2, a raw material gas nozzle 51a, a reaction gas nozzle 51b, and a purge gas nozzle 51c are arranged in the region 12c clockwise as viewed from above the reaction tube 12. The source gas nozzle 51a and the purge gas nozzle 51c are connected to an organic zirconium gas (tris (dimethylamino) cyclopentadienyl / zirconium gas) storage source 55a and a purge gas (nitrogen (N ₂ ) gas) storage source 55c, respectively. ing. On the other hand, the reaction gas nozzle 51b is connected to an oxygen gas storage source 55b via an ozone generation system 60 for generating high-concentration ozone gas from oxygen gas.

That is, the ozone gas generation system 60 includes an ozone generator (generator) 61 that generates ozone from oxygen gas and an ozone concentrator (booster) 62 that concentrates the ozone gas generated by the ozone generator 61. The configuration is arranged from the side toward the reactive gas nozzle 51b side. When a mixed gas of oxygen gas and ozone gas is called “reaction gas”, the ozone generator 61 generates ozone gas so that the concentration of ozone gas in the reaction gas is, for example, about 200 g / Nm ³ . Then, the ozone concentrator 62, the ozone gas in the range of 300g ^/ Nm ³ ~500g ^/ Nm 3 is (as concentrated) configured as obtained from the reaction gas. That is, the ozone concentrator 62 by the control signal of the control unit 100 will be described later, the concentration of ozone gas ⁽ⁱⁿ the range of ^{300g / Nm 3 ~500g / Nm 3} ) optionally any adjustments to process gas flow rate (1Slm～20slm ). The ozone concentrator 62 is specifically a high concentration ozone concentrator manufactured by Iwatani Corporation.

  In FIG. 1 and FIG. 2, 52 is a gas discharge port, which is formed at a plurality of locations along the length direction of the wafer boat 11 on the side surface of each gas nozzle 51 a to 51 c on the slit 17 side. 1 and 2, 53 is a valve, and 54 is a flow rate adjusting unit, which is configured to supply nitrogen gas not only to the purge gas nozzle 51c but also to other gas nozzles 51a and 51b.

  As shown in FIG. 1, an exhaust port 21 is formed in a portion of the side wall of the flange portion 18 facing the above-described slit 17 so as to communicate with a region between the inner tube 12 b and the outer tube 12 a. A vacuum pump 24 is connected to an exhaust path 22 extending from the exhaust port 21 via a pressure adjusting unit 23 such as a butterfly valve. On the lower side of the flange portion 18, a lid 25 formed in a substantially disc shape is provided so as to be in airtight contact with the flange surface, which is the outer peripheral portion on the lower end side of the flange portion 18, in the circumferential direction. The lid body 25 is configured to be movable up and down together with the wafer boat 11 by a boat elevator (not shown). In FIG. 1, 26 is a heat insulator, and 27 is a rotating mechanism such as a motor.

  As shown in FIG. 1, this vertical heat treatment apparatus is provided with a control unit 100 composed of a computer for controlling the operation of the entire apparatus. A program for performing processing is stored. This program is installed in the control unit 100 from the storage unit 101 which is a storage medium such as a hard disk, a compact disk, a magneto-optical disk, a memory card, and a flexible disk.

  Next, a film forming method as an operation of the above-described embodiment will be described with reference to FIGS. First, the outline of this film forming method will be described. In the present invention, a thin film (zirconium oxide film) is formed by repeating a film forming cycle for alternately supplying an organic material gas and a reaction gas containing ozone gas a plurality of times. A film is being formed.

  Next, the details of the film forming method will be described in detail. First, the wafer boat 11 loaded with a large number of wafers W is air-tightly introduced into the reaction tube 12 that has already been heated to the film formation temperature, and the inside of the reaction tube 12 is evacuated and then set to a processing pressure. . Next, when the source gas is supplied into the reaction tube 12 (step S1), the source gas is adsorbed on the surface of each wafer W as shown in FIG.

Thereafter, after the supply of the source gas is stopped and the inside of the reaction tube 12 is evacuated (step S2), a purge gas is supplied into the reaction tube 12 (step S3) as shown in FIG. The atmosphere in the tube 12 is replaced. Thereafter, as shown in FIG. 6, high-concentration ozone gas is supplied into the reaction tube 12 set to the processing pressure (evacuated by the vacuum pump 24) (step S4). That is, ozone gas contained in the processing gas at a high concentration of 500 g / Nm ³ is supplied to the wafer W through the ozone generator 61 and the ozone concentrator 62. The flow rate of the processing gas is 6 to 20 slm.

  When the ozone gas comes into contact with the adsorption layer 91 on the wafer W, as shown in FIG. 6, the zirconium element contained in the adsorption layer 91 is oxidized, and zirconium oxide is generated to form a reaction layer 92. Further, impurities such as carbon, hydrogen or nitrogen contained in the adsorption layer 91 are oxidized and desorbed from the adsorption layer 91 as a by-product gas. Here, since the concentration of the ozone gas contained in the processing gas is extremely high, and further, a large number of wafers W are arranged in the wafer boat 11 in multiple stages. Since a large amount of by-product gas is generated, this by-product gas stays in the reaction tube 12. Therefore, if the inside of the reaction tube 12 is only replaced by a normal method thereafter, the by-product gas is not exhausted from the reaction tube 12 and remains in the reaction tube 12. When the by-product gas remains in the reaction tube 12 in this way, the organic raw material gas supplied in another subsequent film forming cycle reacts with the by-product gas, and a reaction product generated by this reaction occurs. Things are taken into the reaction layer 92.

  Therefore, in the present invention, a step of favorably discharging the by-product gas that stays in the reaction tube 12 is performed as follows. Specifically, the supply of the reaction gas is stopped and the inside of the reaction tube 12 is evacuated (the pressure adjustment unit 23 is fully opened) for the set time (for example, 20 seconds) (step S5). . In this previous step, a part of the by-product gas that stays in the reaction tube 12 is discharged toward the exhaust port 21, but the remaining by-product gas still remains in the atmosphere in the reaction tube 12.

  Next, while the inside of the reaction tube 12 is kept in a drawn state, or after the inside of the reaction tube 12 is set (returned to) the processing pressure, a subsequent step of supplying purge gas into the reaction tube 12 is performed for a set time (for example, 20 (Step S6). By this subsequent step, as shown in FIG. 7, the by-product gas still remaining in the atmosphere in the reaction tube 12 is diluted with the purge gas and discharged from the reaction tube 12 together with the purge gas. Therefore, the concentration of the by-product gas staying in the reaction tube 12 is lower than that immediately after the adsorption layer 91 is oxidized. In this example, the total time of the preceding step and the succeeding step is 40 seconds.

  Subsequently, the atmosphere replacement step including the preceding step and the subsequent step described above is performed until the set number n (n: natural number) is reached (step S7). In this example, the atmosphere replacement step is performed five times in total. The total time t devoted to these five atmosphere replacement steps is, for example, 200 seconds ((20 + 20) × 5). As the atmosphere replacement step is repeated, the concentration of the by-product gas staying in the atmosphere in the reaction tube 12 decreases, and when the atmosphere replacement step is performed five times, the by-product gas in the reaction tube 12 The concentration is lowered to a level that does not react with the organic source gas supplied in the film forming cycle or does not adversely affect the reaction. When the organic source gas supply step and the reaction gas supply step described above are alternately set times k (k: natural number) while replacing the atmosphere in the reaction tube 12, in this example, the reaction layer 92 is obtained by repeating 30 times. A thin film is formed by laminating (step S8).

  According to the above-described embodiment, when forming the thin film by alternately supplying the organic source gas and the ozone gas to the wafer W, after supplying the reaction gas containing the ozone gas, before supplying the organic source gas The following findings were found regarding the atmosphere replacement process performed in Specifically, as shown in the examples described later, the amount (thickness) of the thin film decreases as the time t devoted to the atmosphere replacement step increases. In other words, when the time t is not so long, impurities other than the compounds constituting the thin film are easily taken into the thin film. The reason why the impurities are taken into the thin film is based on other elemental analysis and the like, and after the impurities are once discharged from the reaction layer 92, they are retained in the processing atmosphere, and another film formation is performed subsequently. It was found that the reaction layer 92 was again taken in as a by-product due to an abnormal reaction with the organic source gas supplied in the cycle. Furthermore, it has been found that the correlation between the time t spent in the atmosphere replacement step and the film formation amount is a phenomenon that becomes noticeable only when a reaction gas containing ozone gas at a high concentration is used. That is, if high-concentration ozone gas is used in order to reduce the concentration of impurities contained in the thin film after film formation, the concentration of impurities contained in the thin film increases conversely, and such a phenomenon remains in the reaction tube 12. It was found to be caused by the product gas. Therefore, in order to discharge the by-product gas staying in the atmosphere in the reaction tube 12, the set number of times n (atmosphere replacement process time t) for performing the atmosphere replacement process including the preceding step and the subsequent step is set as described above. doing. Therefore, since it can suppress that an impurity is taken in into the reaction layer 92, the thin film of favorable film quality can be obtained.

Therefore, in order to obtain a thin film having good film quality, for example, the heating temperature in the reaction tube 12 does not need to be so high, so that the occurrence of thermal damage to other devices formed on the wafer W can be suppressed. In addition, when a thin film having a good film quality is formed, the settable range (lower limit value) of the heating temperature in the reaction tube 12 is widened. Therefore, the method of the present invention can increase the degree of freedom of the process. I can say that.
The present invention is directed to a batch furnace that performs film formation processing on a large number of wafers W when performing the atmosphere replacement step over a long period of time as described above. Therefore, a thin film having good film quality can be obtained while suppressing a decrease in throughput.

  Here, the correlation between the total time t spent in each of the previous step and the subsequent step and the impurities remaining in the reaction layer 92 will be described in detail. That is, in general ALD, an atmosphere replacement process for replacing the processing atmosphere when switching between the organic source gas and the ozone gas does not take much time. The reason for this is that it is sufficient to set a certain amount of time in order to avoid mixing the organic source gas and ozone gas in the processing atmosphere. On the other hand, if too much time is spent in the atmosphere replacement step, it leads to a decrease in throughput. End up. Further, as can be seen from the examples described later, even with a normal ozone gas concentration, the effect of the present invention cannot be expected so much even if a long time is spent in the atmosphere replacement step. Therefore, in general, in the atmosphere replacement step, the time is set so that the gas can be sufficiently exhausted from the processing atmosphere. Specifically, the time for the atmosphere replacement step is generally about several tens of seconds.

  However, in the present invention, as shown in the examples to be described later, when a reaction gas containing ozone gas at a high concentration is used, a reaction between a by-product gas staying in the reaction tube 12 and an organic material gas is caused. It has been found that by-products that are generated are taken into the reaction layer 92. Therefore, in the present invention, in order to discharge the by-product gas that stays in the atmosphere in the reaction tube 12 in the atmosphere replacement process that is performed after the supply of the reaction gas is stopped and before the supply of the organic material gas is started. , Have spent some time long. FIG. 8 shows a correlation between the film formation amount D of the thin film and the time (total time of the previous step and the subsequent step) t spent in the atmosphere replacement step, and is shown in FIG. It is schematically described based on actual measurement values. Therefore, in FIG. 8, the attenuation rate (curve curve) of the film formation amount D is also schematically described.

  The variation pattern of the film formation amount D shown in FIG. 8 indicates whether the wafer W to be measured is placed at the top of the arrangement region in the height direction of the wafer boat 11 or at the center, or at the bottom. It is hard to say that they are completely the same, but there is virtually no difference. Therefore, in the present invention, from the viewpoint of clarifying the technical contents, it is assumed that the fluctuation pattern of the film formation amount D shown in FIG. 8 is in the central region in the vertical direction of the wafer boat 11. The central region refers to a region belonging to the central equally divided region, for example, when the array region of the wafer boat 11 is equally divided into three in the vertical direction.

  Focusing on FIG. 8, the film formation amount D is a thick film at 40 seconds, which is a time t set in general ALD, while the time t increases until the time t reaches 200 seconds. It decreased with time. Thereafter, when the time t reaches 200 seconds or slightly exceeds 200 seconds (about 10 seconds), the film formation amount D becomes a substantially constant value. Therefore, as described above, when the time t is not so long, the impurities are taken into the reaction layer 92. On the other hand, the longer the time t is, the harder the impurities are taken into the thin film. .

  Here, when the reduction rate of the film formation amount D is examined, the reduction rate decreases with the passage of time t. When the time t reaches 200 seconds, the reduction rate (value per 80 seconds) of the film formation amount D is less than 1.5% (specifically, as shown in the examples described later). 1.285%), and it can be said that the thin film is substantially free of impurities, so that a thin film having good film quality can be obtained.

  In order to further reduce impurities in the thin film on the wafer W, the time t is preferably 200 seconds or more. On the other hand, from the viewpoint of shortening the heat treatment time, it is preferable that the time t is short. From this viewpoint, it can be said that the time t is preferably at most 150 seconds. That is, assuming that the film formation amount D at which the rate of decrease of the film formation amount D when the time t is increased by 80 seconds is 1.5% or less is D0, in the present invention, the film formation amount D is D0 at time t. An atmosphere replacement step is performed so as to be.

  As the atmosphere replacement step in the present invention described above, it is preferable to repeat the former step and the latter step a plurality of times alternately. However, the former step and the latter step may be performed once. Specifically, in the above-described example, in performing the atmosphere replacement process over 200 seconds, the 20-second pre-step and the 20-second post-step were alternately performed five times, but the 100-second pre-step and The subsequent steps of 100 seconds may be performed once each. The balance between the time spent in the previous step and the time spent in the subsequent step in the atmosphere replacement step is preferably 1: 1, but may be set to 1: 3 to 3: 1.

  Moreover, when setting the time t of the atmosphere replacement step as described above, it is preferable to set it for all of the film formation cycles performed many times, but the film quality is good over the film thickness direction of the thin film. In order to obtain the above, the film forming cycle may be performed for 80% or more of the film forming cycles. For example, when fifteen film formation cycles are performed, for example, for the 12 film formation cycles, 200 atmospheres are each allocated to the atmosphere replacement step, and the remaining three film formation cycles are performed. For each, the atmosphere replacement step may be performed for 40 seconds each.

The organic source gas may be a gas containing carbon, and another example of the zirconium-based gas is TEMAZ (tetrakisethylmethylaminozirconium) gas. In addition, instead of zirconium-based gas, for example, Hf (hafnium) -based gas, Sr (strontium) -based gas, Al (aluminum) -based gas, Ti (titanium) -based gas, or Si (silicon) -based gas may be used as the organic source gas. May be used. These gases are used, for example, in a state where organic substances are combined. An example of each organic source gas is TEMHF (tetrakisethylmethylaminohafnium) gas, Sr (THD) ₂ (strontium bistetramethylheptanedionate) gas, TMA (trimethylaluminum) gas, Ti (MPD). ) (THD) (titanium methylpentanedionatobistetramethylheptaneedionato) gas, aminosilane gas.

  Further, when supplying the purge gas into the reaction tube 12, instead of using the purge gas nozzle 51c dedicated to the purge gas, the source gas nozzle 51a or the reaction gas nozzle 51b may be used as the purge gas nozzle 51c. Furthermore, instead of providing the reaction tube 12 vertically, a configuration may be adopted in which the wafer boat 11 is loaded and unloaded from the left-right direction by being arranged horizontally.

Next, examples obtained by the present invention described above will be described.
(Example 1)
FIG. 9 shows the result of confirming the concentration of ozone gas in the processing gas and the oxidizing power of the processing gas. Specifically, a process gas having various ozone gas concentrations was supplied to the surface of the bare silicon wafer to oxidize the surface of the bare silicon wafer. Thereafter, the oxidized bare silicon wafer was immersed in an aqueous hydrogen fluoride solution, and the film thickness of the bare silicon wafer dissolved in the aqueous hydrogen fluoride solution was measured. That is, the silicon oxide film formed by oxidation of the bare silicon wafer is dissolved in the hydrogen fluoride aqueous solution, while the bare silicon wafer itself is not dissolved in the hydrogen fluoride aqueous solution (or the dissolution rate is extremely slow). By measuring, it can be said that the film thickness (strength of oxidizing power of the processing gas) of the bare silicon wafer oxidized by the processing gas can be measured.

As a result, as shown in FIG. 9, it was found that when the concentration of ozone gas in the processing gas is 500 g / Nm ³ , the oxidizing power of the processing gas is stronger than that of 200 g / Nm ³ . In FIG. 9, the natural oxide film formed on the bare silicon wafer is shown as “unprocessed”.

(Example 2)
In Example 2, an oxide film was formed using processing gases having different ozone gas concentrations, and the electrical resistance (sheet resistance) of the oxide film was evaluated. As a result, as shown in FIG. 10, when the concentration of ozone gas in the processing gas was 500 g / Nm ³ , the oxidizing power of the processing gas was stronger than that of 200 g / Nm ³ .

(Example 3)
In Example 3, an organic source gas and a reactive gas (mixed gas of oxygen gas and ozone gas) described above are alternately supplied to form a zirconium oxide film, and then impurities in the film thickness direction of the zirconium oxide film The concentration of (carbon element) was measured. In this experiment, a processing gas whose ozone gas concentration was set to 500 g / Nm ³ and a processing gas set to 200 g / Nm ³ were used. In any case of ozone gas concentration, the atmosphere replacement process performed after the process gas supply process was performed under a common condition in which the 20-second pre-stage and the 20-second post-stage were performed once.

As a result, as shown in FIG. 11, when the ozone gas concentration was 500 g / Nm ³ , many impurities remained in the zirconium oxide film as compared with 200 g / Nm ³ . Therefore, when the concentration of ozone gas is 500 g / Nm ³ , it is considered that impurities contained in the organic source gas are once released into the atmosphere and then taken into the zirconium oxide film again. Therefore, in this experiment, the time t (specifically 40 seconds) devoted to the atmosphere replacement step is insufficient to discharge the by-product gas from the processing atmosphere when the ozone gas concentration is set to 500 g / Nm ^3. You can see that

Example 4
In Example 4, when the zirconium oxide film was formed by the method of alternately supplying the organic source gas and the reaction gas a plurality of times as described above, the time t of the atmosphere replacement process and the film formation amount of the zirconium oxide film ( Film thickness) Correlation with D was evaluated. The concentration of ozone gas in the processing gas was set to 500 g / Nm ³ .

  As a result, as shown in FIG. 12, the film formation amount D was 5.4 nm thick when the time t was 40 seconds, but the film formation amount D decreased as the time t increased. It was. Therefore, as described above, it can be seen that when the time t is short, the impurity is taken into the zirconium oxide film, and the impurity decreases with the passage of time t thereafter. The uniformity of the film thickness of the zirconium oxide film was almost the same for both the in-plane of the wafer W and between the wafers W. FIG. 12 shows the results of the wafer boat 11 at the upper position, the middle position, and the lower position.

  FIG. 13 shows a zirconium oxide film obtained when the time t is set to 40 seconds in FIG. 12, and the time t is set to 280 seconds (the 20-second pre-step and the 20-second post-step are alternately 7 The results of measuring the concentration of impurities (carbon element) in the film thickness direction for the obtained zirconium oxide film are shown. As can be seen from FIG. 13, the concentration of impurities contained in the zirconium oxide film is lowered by allocating a long time t to the atmosphere replacement step.

(Example 5)
In Example 5, when the concentration of ozone gas in the processing gas was set to 500 g / Nm ³ , the flow rate of the processing gas was fixed to 20 slm, and the time t of the atmosphere replacement process was changed variously to form a zirconium oxide film. The correlation between the time t and the film formation amount D was evaluated. As a result, as shown in FIG. 14, the film formation amount D is a thick film exceeding 3.9 nm at a total time of 40 seconds, which is a time t set in general ALD, while the time t is 200. Until the second, the time t decreased as the time t increased. Thereafter, when the time t was 200 seconds or more, the film formation amount D was settled to about 3.83 nm. FIG. 14 is a graph that is the basis of the schematic diagram shown in FIG. 8 described above.

The following table is the data of FIG. 14 and shows the film formation amount D of the wafer W at the center position accommodated in the reaction tube 12. As can be seen from this table, the decrease rate of the film formation amount D per 80 seconds is less than 1.3% when the time t is 200 seconds, and it can be seen that the thin film is substantially free of impurities. When the time t is 150 seconds or more, the reduction rate of the film formation amount D is 1.5% or less, and it can be said that the impurity concentration is reduced to a level at which there is no problem in applying the thin film to a semiconductor device. Here, the “decrease rate of the film formation amount D” is a value when the time t is increased by 80 seconds, and is specifically calculated as follows. That is, when the film formation amounts D obtained at times t _m and t _{m + 1} (m: positive number) are D _m and D _{m + 1} , respectively, the decrease rate R of the film formation amount D is
R = (D _m −D _{m + 1} ) ÷ D _m ÷ (t _{m + 1} −t _m ) × 80 × 100
It has become. That is, in the calculation formula of the reduction rate R, the reduction rate of the film formation amount D per unit time is calculated, and this reduction rate is converted into a value per 80 seconds.

(table)

(Example 6)
As already described in detail, when a processing gas having an ozone gas concentration of 500 g / Nm ³ is used (more specifically, when the flow rate of the processing gas is set to 20 slm), the film formation amount D is equal to the time t. After the point of time reaching 200 seconds, the value is substantially constant (the rate of decrease of the film formation amount D is substantially zero). When the time t when the film formation amount D reaches a substantially constant value is referred to as “saturation time”, in Example 6, the correlation between the concentration of ozone gas in the processing gas and the saturation time was examined.

Specifically, as shown in FIG. 14 described above, with respect to the correlation between the time t spent in the atmosphere replacement step and the film formation amount D, an experiment was performed by varying the concentration of ozone gas contained in the processing gas, The saturation time was determined for each process gas. FIG. 15 shows the results obtained in this experiment. When the concentration of ozone gas is 500 g / Nm ³ , the saturation time is 200 seconds as described above. On the other hand, when the ozone gas concentration is 300 g / Nm ³ and 200 g / Nm ³ , the saturation time is 120 seconds and 140 seconds, respectively.

Therefore, it can be seen that the effect of increasing the time t of the atmosphere replacement step becomes more significant as the concentration of ozone gas contained in the processing gas increases. On the other hand, it can be seen that with the conventional ozone gas concentration (200 g / Nm ³ ), the effect of discharging impurities contained in the zirconium oxide film cannot be expected so much even if the time t is extended. That is, setting the time t of the atmosphere replacement step as in the present invention can be said to be effective only when high-concentration ozone gas is used.

W Wafer 11 Wafer boat 12 Reaction tube 21 Exhaust ports 51a to 51c Gas nozzle 52 Gas discharge port 60 Ozone gas generation system D Film formation amount

Claims (9)

A film forming cycle for sequentially supplying a reaction gas containing an organic source gas and ozone gas to a plurality of substrates held in a shelf shape on a substrate holder in a reaction tube is repeated a plurality of times, and the organic source gas and In a film forming method of laminating a reaction product with ozone gas on a substrate,
The film formation cycle includes an atmosphere including a pre-stage for evacuating the inside of the reaction tube and a post-stage for supplying an inert gas after the supply of the reaction gas is stopped and before the supply of the organic source gas is started. Including a replacement step,
The film formation amount obtained by carrying out the film formation cycle by setting the previous step and the subsequent step of the atmosphere replacement process one time each at the same time is defined as D, and the total amount to be applied to the previous step and the subsequent step In the graph showing the relationship between the time t and the film formation amount D, the film formation amount D decreases as the time t increases, and when the time t increases 80 seconds, the decrease rate of the film formation amount D is 1.5% or less. If the film-forming amount D becomes D0,
The film forming method is characterized in that the atmosphere replacement step is performed so that a film forming amount D when the film forming cycle is performed becomes D0.   2. The atmosphere replacement step in a film forming cycle corresponding to a number of times of 80% or more among the film forming cycles repeated a plurality of times is characterized in that the time t is set to 200 seconds or more. The film-forming method of description.   2. The film forming method according to claim 1, wherein the time t is set to 200 seconds or more in each atmosphere replacement step in each film forming cycle. The film forming method according to claim 1, wherein the concentration of ozone gas contained in the reaction gas is 300 g / Nm ³ or more. A film forming cycle for sequentially supplying a reaction gas containing an organic source gas and ozone gas to a plurality of substrates held in a shelf shape on a substrate holder in a reaction tube is repeated a plurality of times, and the organic source gas and In a film forming apparatus for laminating a reaction product with ozone gas on a substrate,
After the supply of the reaction gas is stopped and before the supply of the organic material gas is started, an atmosphere replacement process including a pre-step for evacuating the inside of the reaction tube and a post-step for supplying an inert gas is then formed. A control unit that outputs a control signal to perform as part of the cycle,
The film formation amount obtained by carrying out the film formation cycle by setting the previous step and the subsequent step of the atmosphere replacement process one time each at the same time is defined as D, and the total amount to be applied to the previous step and the subsequent step In the graph showing the relationship between the time t and the film formation amount D, the film formation amount D decreases as the time t increases, and when the time t increases 80 seconds, the decrease rate of the film formation amount D is 1.5% or less. If the film-forming amount D becomes D0,
The film forming apparatus, wherein the control unit outputs a control signal so as to perform the atmosphere replacement step so that a film forming amount D when the film forming cycle is performed becomes D0.   The control unit outputs a control signal so that the time t in each atmosphere replacement step of the film formation cycle corresponding to the number of times of 80% or more among the film formation cycles repeated a plurality of times is set to 200 seconds or more. The film forming apparatus according to claim 5.   6. The film forming apparatus according to claim 5, wherein the time t is set to 200 seconds or more in the atmosphere replacement step in each film forming cycle. The film forming apparatus according to claim 5, wherein a concentration of ozone gas contained in the reaction gas is 300 g / Nm ³ or more. A storage medium storing a computer program that runs on a computer,
5. A storage medium, wherein the computer program includes steps so as to carry out the film forming method according to claim 1.