JP2000183050A - Method for evaluating vaporization amount of liquid raw material in film forming processing system - Google Patents

Abstract

(57) Abstract: Provided is a method for evaluating a vaporization amount of a liquid material of a film formation processing system, which is capable of evaluating a degree of mist of a vaporized film formation gas remaining. SOLUTION: A pressurized liquid raw material 10 is supplied to a vaporizing means 22 while controlling a flow rate to vaporize the liquid raw material 10, thereby forming a film forming gas. To be processed W
A first step of flowing said film forming gas into said film forming apparatus for a predetermined time in a method for evaluating a vaporization amount of a liquid material in a film forming system for forming a film on said liquid material; A second step of stopping and stopping the source gas passage downstream of the vaporizing means and the inside of the film forming apparatus, and a third step of carrying a monitor object into the film forming apparatus. A fourth step of allowing the loaded monitor object to stand for a predetermined time, and a fifth step of evaluating the amount of vaporization of the liquid material based on a film formed on the monitor object. Having. This makes it possible to evaluate the degree to which the vaporized film forming gas is misted and remains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the amount of vaporized liquid material used in a film forming system for forming a film such as tantalum oxide.

[0002]

2. Description of the Related Art In general, in order to manufacture a semiconductor device, a film forming process and a pattern etching process are repeatedly performed on a semiconductor wafer to manufacture a desired device. The specifications are becoming stricter year by year as the degree of integration increases. For example, very thin oxide films such as insulating films and gate insulating films of capacitors in devices, and furthermore for electrode films and wiring films, etc. Thinning is required.

For example, taking an insulating film as an example, a silicon oxide film, a silicon nitride film, or the like has been used as an insulating film in the past. Recently, a metal oxide film has been used as a material having better insulating properties. For example, tantalum oxide (Ta)
₂ O ₅ ) tends to be used. It is known that even though this metal oxide film is thin, it exhibits highly reliable insulation properties, and that after the formation of this metal oxide film, the surface can be modified to further improve the insulation properties. And
The technique is disclosed in Japanese Patent Application Laid-Open No. 2-283022.

In order to form the metal oxide film, for example, a case of forming tantalum oxide will be described. As disclosed in the above publication, a liquid metal alkoxide of tantalum (Ta ( OC ₂ H ₅ ) ₅ )
This is supplied while bubbling with nitrogen gas or the like to maintain the semiconductor wafer at a process temperature of, for example, about 400 ° C., and to perform CVD (Chemical V) under a vacuum atmosphere.
A tantalum oxide film (Ta ₂ O ₅ ) is laminated by apor deposition.

[0005]

However, as described above, the specifications of semiconductor devices have become strict,
At the time of film formation by CVD, the film thickness must be accurately controlled, but it is difficult to precisely control the supply amount of the raw material liquid by the above-described supply method using bubbling. Therefore, as another method of supplying a raw material liquid, a pressurized raw material liquid is supplied to a liquid mass flow controller (Liquid Mass Flow Control).
er) while controlling the flow rate and supplying it to a vaporizer to vaporize it.
Attempts have been made to accurately control the supply amount of the raw material liquid by introducing the film-forming gas formed here into the processing apparatus.

In this case, although the temperature of the gas passage downstream of the vaporizer is kept so that the vaporized film forming gas does not condense and reliquefy, the film forming gas condenses in the gas passage due to various causes. It is difficult to avoid that the mist adheres to the inner wall of the gas passage or the like in the form of a mist. In this case, too, the amount of the film forming gas (the amount of the liquid raw material) actually introduced into the processing apparatus is reduced. It was difficult to grasp accurately. Therefore, even if the generation of mist as described above is tolerated,
If it is possible to recognize how much of the liquid raw material that has flowed through the liquid mass flow controller remains as a mist in a gas passage or the like without disassembling the pipes or the like, the amount of liquid that has actually flowed into the film forming apparatus can be recognized. It is possible to evaluate the gas passage system by obtaining the film gas amount or the ratio, but at present, no such evaluation method has been proposed. The present invention has been devised in view of the above problems and effectively solving them. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for evaluating the amount of vaporized liquid raw material in a film forming system, which can evaluate the degree of mist of a vaporized film forming gas remaining.

[0007]

According to a first aspect of the present invention, a film forming gas is formed by supplying a pressurized liquid raw material to a vaporizing means while controlling the flow rate to vaporize the liquid raw material. In the vaporization amount evaluation method of the liquid material amount of a film formation processing system in which a gas is introduced into a film formation apparatus through a source gas passage that is heated and kept warm, and a film formation process is performed on an object to be processed,
A first step of flowing the film forming gas into the film forming apparatus for a predetermined time; and stopping the supply of the liquid raw material to evacuate the material gas passage downstream of the vaporizing means and the inside of the film forming apparatus. A second step of loading the monitor object into the film forming apparatus, a fourth step of leaving the carried monitor object for a predetermined time, A fifth step of evaluating a vaporization amount of the liquid raw material based on a film formed on the monitoring target object.

As described above, if the mist of the film forming gas remains on the inner wall of the source gas passage or the inner wall of the film forming apparatus, the thickness corresponding to the mist amount is formed on the surface of the monitor object in the fifth step. The deposited film is deposited, and depending on the state of the deposited film,
It is possible to evaluate how much of the liquid material that has flowed is actually supplied into the processing apparatus and contributes to film formation. In this case, as set forth in claim 2, the source gas passage is maintained at a temperature higher than the liquefaction temperature of the liquid source. Claim 3
As described in the above, a metal alkoxide can be used as the liquid raw material.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for evaluating the amount of vaporized liquid material in a film forming system according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic overall configuration diagram showing a film formation processing system for performing a vaporization amount evaluation method according to the present invention. Here, tantalum oxide (T
a ₂ O ₅ ) is formed by CVD. The film forming system 2 mainly includes a film forming apparatus 4 and a material supply system 6 that supplies a liquid material as a film forming gas to the film forming apparatus 4 in a vaporized state.

The raw material supply system 6 has a closed raw material tank 12 for storing a liquid raw material 10, for example, a metal alkoxide of (Ta (OC ₂ H ₅ ) ₅ ) as a raw material of a metal oxide film. This tank 12 has a heater 14
And a temperature at which the raw material 10 can easily flow, for example, 20 to
It is heated to about 50 ° C. Further, in the liquid raw material 10, for example, an appropriate amount of alcohol is added as a reaction accelerator. In the gaseous phase portion of the raw material tank 12, the tip of a pressurizing tube 16 is introduced from above.
Is provided with a flow controller 18 such as a mass flow controller and an on-off valve 20, for example, He gas as a pressurized gas.
The gas can be introduced into the gas phase in the raw material tank 12.

The raw material tank 12 and the inlet of the vaporizer 22 as vaporizing means are connected by a liquid raw material supply passage 24 made of, for example, a stainless steel tube. A source gas passage 26 made of, for example, a stainless tube is provided so as to communicate with the ceiling. The raw material inlet 24A of the supply passage 24 is immersed in the liquid raw material 10 in the tank 12 and located near the bottom so that the liquid raw material 10 can be conveyed under pressure into the passage 24. The liquid source supply passage 24 is provided with an on-off valve 29 and a liquid mass flow controller 28 in the middle thereof so that the supply amount of the liquid source 10 to the vaporizer 22 can be controlled. A purge gas introduction pipe 30 for introducing, for example, N ₂ gas as an inert gas for purging is connected to the liquid supply passage 24 on the upstream side of the liquid mass flow controller 28.
An on-off valve 32 is provided in the middle of the process.

The liquid material supply passage 24 from the material tank 12 to the vaporizer 22 has a liquid flow rate of, for example, 5 mg /
Since the diameter is very small, such as about min, a narrow pipe having an inner diameter of about 1 to 2 mm is used. On the other hand, the material gas passage 26 downstream of the vaporizer 22 has a large inner diameter because a film-forming gas in a gas state flows therethrough. For example, a pipe having a length of about 10 to 20 mm is used. An on-off valve 36 for shutting off the supply of the film forming gas is provided in the source gas passage 26 immediately downstream of the vaporizer 22. In the raw material gas passage 26 on the downstream side of the vaporizer 22, a heater 34 made of, for example, a tape heater, including the on-off valve 36, is wound.
The temperature is maintained at a temperature higher than the liquefaction temperature of the film forming gas and lower than the decomposition temperature, for example, in the range of 150 ° C. to 180 ° C. A gas introduction pipe 40 for vaporization is connected to the vaporizer 22 so that, for example, He gas is supplied as a gas for vaporization while controlling the flow rate by a flow rate controller 38. In addition, the gas introduction pipe for vaporization 4
An opening / closing valve 42 is also provided in the middle of 0.

On the other hand, the film forming apparatus 4 has a processing container 44 formed into a cylindrical shape by, for example, aluminum. Around the center of the bottom portion 44A of the processing container 44,
An exhaust port 46 is provided, and an on-off valve 48 and a vacuum pump, for example, a turbo molecular pump 50 and a dry pump 52 are interposed in the exhaust port 46, and a vacuum exhaust system 53 is connected to the exhaust port 46. The inside of the container can be evacuated. A plurality of, for example, about four exhaust ports 46 are provided on the same circumference at equal intervals on the container bottom 44A (only two are shown in the illustrated example), and the exhaust ports 46 are commonly evacuated. A disc-shaped mounting table 54 made of a non-conductive material, for example, alumina is provided in the processing container 44, and, for example, a semiconductor wafer W as an object to be processed is mounted on the mounting table 54. I have.

In the mounting table 54, for example, a carbon resistance heating element 56 coated with SiC is embedded, and the semiconductor wafer mounted on the upper surface side can be heated to a desired temperature. Has become. The wafer may be heated by using a heating lamp such as a halogen lamp instead of the resistance heating element 56 as a means for heating the wafer. The upper portion of the mounting table 54 is configured as, for example, an electrostatic chuck (not shown) made of ceramics. The Coulomb force generated by the electrostatic chuck 58 sucks and holds the wafer on the upper surface. I have. Further, a mechanical clamp may be used in place of the electrostatic chuck 58. The processing container 44
A shower head 60 is air-tightly mounted on the ceiling of the mounting table 54, and the shower head 60 is provided so as to oppose so as to cover substantially the entire upper surface of the mounting table 54. The inlet of the shower head 60 is provided with the raw material gas passage 2.
6 are joined to each other so that a film-forming gas or the like is introduced into the processing container 44 in a shower shape. And
A load lock chamber 64 that can be evacuated through a gate valve 62 is joined to the processing container 44.

Next, the method of the present invention performed using the film forming system configured as described above will be described. The method of the present invention evaluates the degree of vaporization of the liquid raw material 10, and does not actively perform a film forming process on a semiconductor wafer. In general, the method of the present invention is as follows. A film forming gas is flowed into a film forming apparatus for a certain period of time under the same conditions as actual film forming conditions. And seal the inside. And
In this state, the mist adhering to the inner wall of the source gas passage or the inner wall of the film forming apparatus is re-evaporated into a film forming gas during this standing, and the film adheres to the wafer. Become. After leaving for a certain period of time, the monitor wafer is taken out of the film forming apparatus, and if there is a film, and if there is a film, the thickness is measured to evaluate the amount of vaporization. As a matter of course, if the vaporization amount is 100%, no mist is present in the source gas passage 26 and the like, so that no film is formed on the monitor wafer.

Next, the method of the present invention will be specifically described with reference to the flowchart shown in FIG. First, an N ₂ gas is purged in order to remove impurity gas remaining in each passage, the processing container 44 of the film forming apparatus 4, and the like. For example, the open / close valves 32, 36, and 48 provided in the purge gas introduction pipe 32, the source gas passage 26, and the vacuum exhaust system 53 are opened, and the liquid mass flow controller 28, the vaporizer 22, the source gas passage 26, and the film are formed. N ₂ gas is introduced into the shower head 60 and the processing container 44 of the apparatus 4 (S1). This allows
Eliminate impurity gases in the gas flow path. At this time, it goes without saying that the turbo molecular pump 50 and the dry pump 52 are driven to evacuate.

Next, the on-off valve 32 of the purge gas introduction pipe 30
Is closed to stop purging of N ₂ gas. Then, the pressurizing pipe 16, the liquid material supply passage 24, and the vaporizing gas introducing pipe 40
The opening / closing valves 20, 29 and 40 provided in the above are opened to vaporize the liquid raw material, and the formed film forming gas flows into the processing apparatus 4 (S2). That is, by introducing a pressurized gas such as He gas whose flow rate is controlled into the raw material tank 12, the alcohol-containing liquid raw material 10 made of liquid Ta (OC ₂ H ₅ ) ₅ is subjected to liquid mass flow control at this pressure. Container 28
The pressure inside the liquid source supply passage 24 is controlled while the flow rate is controlled. The supply amount of the pressurized gas at this time is, for example, several hundreds.
SCCM, and the supply amount of the liquid raw material 10 is, for example, about several mg / min, which is the same supply amount as that during actual film formation. Further, since the liquid raw material 10 in the raw material tank 12 is heated by the heater 14 and has reduced viscosity, the liquid raw material supply passage 24 can be pressure-fed relatively smoothly. The pumped liquid raw material is, for example, 200 to 500 SCC in the vaporizer 22 in the same manner as in actual film formation.
The gas is vaporized by a vaporizing gas such as He gas whose flow rate is controlled to about M to form a film forming gas.
Flows downstream, and is introduced into the shower head 60 of the processing container 44. At this time, since the raw material gas passage 26 is heated to a predetermined temperature higher than the reliquefaction temperature, for example, about 130 ° C., by the heat retaining heater 34, the vaporized film forming gas may be reliquefied or may be thermally decomposed. Although it is possible to flow to the shower head 60 in a state where it is considerably suppressed, it is inevitable that the mist becomes slightly mist and adheres to the inner wall of the passage. The film forming gas reaching the shower head 60 is transferred from the shower head 60 to the processing container 44.
And exhausted through a vacuum exhaust system 53.

At this time, it is not necessary to place a wafer on the mounting table 54, but the resistance heating element 56 allows the mounting table 5 to be mounted.
4 at the same temperature as in the actual film forming process, for example, 250 to
It is set within a range of about 450 ° C. Further, the pressure in the processing container 44 is set to the same pressure as in the actual film forming process, for example, in the range of about 0.1 to several Torr, for example, about 3.0 Torr. Thus, in this step, a film forming gas is flown under the same conditions as in the actual film forming process, regardless of whether or not to form a film on the wafer. by this,
Although the whole is heated, the raw material gas passage 2
The mist of the deposition gas slightly adheres to the inner wall 6, the inner wall of the shower head 60, the inner wall of the processing container 44, and the like. The film forming gas flows for a predetermined time, for example, the same time as the actual film forming time, thereby completing the first step.

Next, except for the on-off valve 48 of the vacuum evacuation system 53, the other on-off valves 20, 29, 36, and 42 are closed, and the supply of the liquid raw material 10 is stopped. It stops, and in this state, only the evacuation system 53 is driven to continue evacuation (S3). Thereby, the inside of the processing vessel 44 and the raw material gas passage 2 communicating therewith
The inside of the chamber 6 is evacuated to remove the film forming gas remaining inside. At this time, the inside of the processing container 44 is evacuated until the pressure becomes substantially the same as that of the load lock chamber 64 maintained in a vacuum state in advance, and the second step is completed by this evacuation.

Next, the inside of the processing container 44 is placed in the load lock chamber 6.
When the pressure becomes the same as that in the monitoring container 4, the monitoring wafer MW is loaded into the processing container 44 via the gate valve 62 opened from the load lock chamber 64 side, and is loaded onto the mounting table 54.
It is placed on the top and held by suction by the Coulomb force of the electrostatic chuck 58 (S4). Then, when the monitoring wafer MW is loaded, the gate valve 62 is closed and the open / close valve 48 of the vacuum exhaust system 53 is also closed, so that the source gas passage 26 and the processing container 44 are in communication with each other. Then, these are completely sealed, and the third step is completed (S5).

Next, the hermetically sealed state is maintained and left for a predetermined time, for example, about one hour (S6). During this time, the temperature of the source gas passage 26 is maintained at the same temperature as that described above, for example, about 130 ° C. by the heater 34, and
The temperature of the wafer 4 and the monitor wafer MW is also maintained at the same level as described above, for example, at a process temperature of 250 to 450 ° C. by the resistance heating element 56. As a result, the mist adhering to the inner wall of the source gas passage 26 and the mist adhering to the inside of the shower head 60, the inner wall of the processing vessel 44, and the like during the flow of the deposition gas are vaporized again. The film forming gas formed by re-vaporization in the source gas passage 26 expands and flows into the processing vessel 44, where the gas formed by re-vaporization in the shower head 60 and the processing vessel 44 is formed. When the film merges with the film gas, the film adheres to the monitor wafer MW, and a film is formed. At this time, the film thickness is naturally set in the raw material gas passage 26 and the shower head 6.
It is proportional to 0 or the amount of mist adhering in the processing container 44. Thus, the fourth step is completed.

Next, if the monitor wafer MW is left for a predetermined time as described above, a fifth step is started, and the monitor wafer MW is taken out of the processing vessel 44 and formed on this surface. The vaporization amount of the liquid raw material 10 is evaluated by measuring the thickness of the formed film (S7). As described above, this film thickness is proportional to the amount of mist adhering to the inside of the raw material gas passage 26, the inside of the shower head 60, and the inside of the processing container 44. Therefore, if there is no film adhering, no mist is present. Therefore, the vaporization amount of the liquid raw material 10 is about 100%. Further, since the film formation rate is generally determined experimentally, the degree of film formation can be determined by the above measurement. It is possible to recognize whether the mist amount remains inside. Therefore, since the flow rate of the entire liquid raw material 10 is known by the liquid mass flow controller 28, the vaporization rate can also be recognized from the ratio of this to the residual mist amount.

If the vaporization amount or vaporization rate of the liquid raw material is determined in this way, when the actual film formation on the product wafer is performed, the vaporization amount and the vaporization rate are taken into account and the amount corresponding to the shortage is considered. By supplying an extra liquid material, it is possible to form a film having a target film thickness. When a large amount of mist accumulates in the source gas passage 26 or the like, the mist can be eliminated by purging the N ₂ gas into the passage as described above. still,
In the above embodiment, the case where a tantalum oxide film is formed using a liquid source made of a metal alkoxide of Ta (OC ₂ H ₅ ) ₅ has been described as an example. However, the method of the present invention is not limited to this. It can be applied to any apparatus for forming a film by using, for example, liquid TEOS, PoCl ₃ ,
The case where a film is formed using a titanium organic material or the like can also be applied. The object to be processed is not limited to a semiconductor wafer, but can be applied to a glass substrate, an LCD substrate, and the like.

[0024]

As described above, according to the method for evaluating the amount of vaporized liquid raw material in the film forming system of the present invention, the following excellent functions and effects can be obtained. A film forming gas obtained by evaporating a liquid material is supplied to the film forming system. Thereafter, the supply of the liquid material is stopped, and the object to be monitored is introduced into the film forming apparatus and allowed to stand. The vaporization amount of the liquid raw material can be evaluated based on the presence / absence, thickness, and the like of the film formed on the processing body without disassembling the film forming system. If the liquid raw material is supplied at the time of actual film formation based on the evaluation result, it is possible to control the film thickness with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic overall configuration diagram showing a film formation processing system for performing a vaporization amount evaluation method according to the present invention.

FIG. 2 is a flowchart showing the steps of the method of the present invention.

[Explanation of symbols]

 2 Film forming system 4 Film forming apparatus 6 Material supply system 10 Liquid material 12 Material tank 22 Vaporizer (vaporizing means) 24 Liquid material passage 26 Material gas passage 28 Liquid mass flow controller 34 Heating heater 44 Processing container 54 Mounting table MW Monitor wafer (object to be monitored)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA03 AA06 AA09 AA11 BA17 BA42 CA04 CA06 EA01 KA23 KA25 KA39 5F045 AB31 AC07 AF19 DP03 EC09 EE02 EF05 GB13 5F083 JA06 PR21

Claims (3)

[Claims] 1. A film forming gas is formed by supplying a pressurized liquid raw material to a vaporizing means while controlling the flow rate to vaporize the liquid raw material, and forming the film forming gas through a heated and maintained raw material gas passage. In the method for evaluating a vaporization amount of a liquid material in a film forming system for performing a film forming process on an object to be processed by being introduced into a film forming apparatus, the film forming gas is flowed into the film forming apparatus for a predetermined time. A first step, a second step of stopping the supply of the liquid source and evacuating the source gas passage downstream of the vaporizing means and the inside of the film forming apparatus, and A third step of loading the processing object, a fourth step of leaving the loaded monitoring target object for a predetermined time, and the liquid source based on a film formed on the monitoring target object. A fifth step of evaluating the amount of vaporization of the film. Method for evaluating the amount of vaporization of liquid raw materials in a physical system. 2. The method according to claim 1, wherein the source gas passage is maintained at a temperature higher than a liquefaction temperature of the liquid source. 3. The method according to claim 1, wherein the liquid raw material is a metal alkoxide.