WO2001076779A1

WO2001076779A1 - Liquid supply unit and purging method in the liquid supply unit

Info

Publication number: WO2001076779A1
Application number: PCT/EP2000/003750
Authority: WO
Inventors: Toshiyuki Nakagawa; Naoyuki Nakamoto; Osamu Nishiyama; Kenji Nakamura; Takashi Tsujiguchi
Original assignee: L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 2000-04-07
Filing date: 2000-04-07
Publication date: 2001-10-18
Also published as: AU4298100A

Abstract

According to the present invention, a liquid supply unit which comprises a supplying line (34) detachably connected with a liquid supply port of a storage container (22), a force-feeding line (40) detachably connected with a force-feeding gas intake port of said storage container, a bypath line (66) for communicating said supplying line and said force-feeding line with each other, a purge gas supply means (46, 48) for supplying a purge gas to said supplying line, and a vacuum evacuation means for vacuum-evacuating the inside of said supplying line, is characterized in that said vacuum evacuation means is made to have a vacuum container (94) constructed such that its inside is depressurized to a predetermined degree of vacuum, and connected with said force-feeding line. In this construction, the vacuum evacuation in the lines can be carried out for a short period of time and stably by use of the vacuum container while a vacuum evacuation apparatus such as a vacuum pump is not directly connected with the lines.

Description

LIQUID SUPPLY UNIT AND PURGING METHOD IN THE LIQUID SUPPLY UNIT

[Detailed Description of The Invention] [Field of the Invention]

The present invention relates to a liquid supply unit for supplying a liquid material for use in a semiconductor-manufacturing process or the likes to a predetermined place of use, and especially to a means for a work for purging the inside of lines which is to be carried out when a storage container storing a liquid material is exchanged. [Prior Arts]

In order to produce microelectronics devices such as semiconductor-integrated devices and liquid crystal panels, it is necessary to form films of various materials on substrates. As methods for forming such films, there have been widely known, in general, PVD (physical vapor deposition) method and CVD (chemical vapor deposition) method.

In a film-forming process mainly based on the, CVD method, by the way, liquid materials such as TiCI4 (titanium tetrachloride), Si(OC2H5)4 (TEOS) are optionally used as a film-forming material. In the prior art, such a liquid material is destined to be supplied to a predetermined point of use, for example, a gasification unit for gasifying the liquid material to a process gas, by means of such a liquid supply unit 1 as shown in Fig. 2.

The illustrated liquid supply unit 1 is essentially composed of a line system to be connected with a small-sized storage container 2 filled with a liquid material, and said line system comprises a supplying line 4 connected with a liquid supply port of the storage container 2 by way of a joint 3 and extending to a place of use and a force-feeding line 7 connected with a force-feeding gas intake port of the storage container 2 by way of a joint 5 and connected with a supply source 6 for a force- feeding gas such as He gas. By sending the force-feeding gas from the force-feeding gas supply source 6 into the storage container 2, in such a construction as mentioned above, the pressure of an inner space of the storage container 2 is elevated and hence the liquid material is forcibly fed from the liquid supply port of the storage container 2 to the supplying line 4.

When the storage container 2 becomes empty, in general, it will be exchanged with a new storage container fully filled with the liquid material. It is necessary, before the storage container 2 is detached from the liquid supply unit 1 , to purge a liquid material which exists between a valve 8 of the supplying line 4 and a valve 9 of the liquid supply port of the storage container 2 by a purge gas such as N2 gas, because such a liquid material for use in a semiconductor-manufacturing process has combustibility and toxicity. After a new container 2 is connected, air gotten in the lines 4, 7 on the exchange of the container must be also purged. Accordingly, the liquid supply unit 1 of the prior art has a system provided therein which comprises a discharging line 10 for sucking and discharging the liquid or the like in the lines 4, 7, a purge gas line 11 for filling a purge gas such as nitrogen gas into the line 4 and a bypath line 12. [Problems Sought for Solution by the Invention]

However, a liquid material for film-forming use exists usually in the form of liquid at normal temperatures and its vapor pressure, is very low due to its higher boiling point, and hence said liquid material may remain in joints and valves as in a liquid phase even if a purging work is carefully carried out by use of such a general purging system as shown in Fig. 2. In a conventional construction, namely, a reachable degree of vacuum of a vacuum evacuation apparatus 13 (in a case of a gas ejector type vacuum generator) used in the discharging line 10 is at most as low as 50 ~ 60 Torr, and even if the gas and the liquid material in the lines are sucked and discharged, in a case of a liquid material such as titanium tetrachloride whose vapor pressure is less than 10 mmHg at normal temperatures, liquid drops may possibly remain in the lines 4, 7, 12, especially in the joints and valves.

By enhancing the reachable degree of vacuum of the vacuum evacuation apparatus 13, this problem can be solved. In fact, an oilless type vacuum pump obtains a reachable degree of vacuum of 1 Torr and an oil type vacuum pump obtains that of 0.01 Torr. However, the oilless type vacuum pump takes a long time until it reaches a predetermined degree of vacuum and the oil type vacuum pump has a problem of "reverse diffusion of an oil component", and either of them is accordingly difficult to use alone.

Further, it has been experimentally pointed out that when a liquid material having a higher corrosiveness is admixed in a vacuum evacuation apparatus, especially an oilless type vacuum pump, any bad influence will be exerted on the performance of said vacuum pump during its operation. For instance, when the liquid material adheres to the inner wall surface of the vacuum pump, such a phenomenon may appear that its reachable degree of vacuum is lowered.

As shown in Fig. 3 (where the same reference numerals are given to the equal or corresponding portions as in Fig. 2), in the prior art, there has been proposed and adopted such a purge system that a gas ejector type vacuum generator 14 (whose reachable degree of vacuum is 30 ~ 60 Torr) and an oilless type vacuum pump 15 (whose reachable degree of vacuum is 1 Torr) are made alternately usable as the vacuum evacuation apparatus and the lines 4, 7, 10, 12 each has a tape heater (not shown) wound thereon. In such a system as mentioned above, the gasification of a liquid material is accelerated by heating the inside of the lines by the tape heaters and the liquid content remaining in the lines is returned to the storage container 2. Vacuum evacuation is carried out by use of the gas ejector type vacuum generator 14 while causing a small amount of a purge gas (nitrogen gas) to flow from the side of a place of use (a position of the reference numeral 16 in Fig. 3). Thereafter, a cycle purge is put in practice, in which the vacuum evacuation by the. vacuum generator 14 and the filling of the purge gas are repeated. After the inside of the lines 4, 7, 12 is finally depressurized to a high degree of vacuum by use of the oilless type vacuum pump 15 and the purge gas is filled, all the valves are closed and the storage container 2 is removed from the lines 4, 7.

In such a purging work as mentioned above, however, there is a problem that a working time becomes longer because the gas ejector type vacuum generator is repeatedly used and the vacuum pump is used which takes a long time until it reaches a stable operation. It is therefore an object of the present invention to provide a liquid supply unit, in which the aforementioned problems in the prior art can be solved, and a purging method.

[Means for Solution of the Problems] In order to achieve the aforementioned purpose, the invention according to claim 1 resides in: a liquid supply unit for supplying a liquid material stored in an exchangeable storage container to a place of use, which comprises: a supplying line detachably connected with a liquid supply port of said storage container for supplying the liquid material in said storage container to the place of use; a force-feeding line detachably connected with a force-feeding gas intake port of said storage container for introducing a force-feeding gas into said storage container so that the liquid material is forcibly fed through said supplying line; a bypath line for communicating said supplying line and said force-feeding line with each other; a purge gas supply means for supplying a purge gas to said supplying line; and a vacuum evacuation means for vacuum-evacuating the inside of said supplying line, wherein said vacuum evacuation means has a vacuum container constructed such that its inside is depressurized to a predetermined degree of vacuum, and connected with said force-feeding line.

In this construction, it is designed that vacuum evacuation in the lines is carried out by use of a vacuum container while the vacuum evacuation apparatus such as the vacuum pump is not directly connected with the lines. By previously depressurizing the inside of the vacuum container and communicating this vacuum container with the lines, namely, it becomes possible to carry out the vacuum evacuation of the lines within a short period of time. Since a liquid material component does not directly flow through the vacuum pump and the likes, any bad influence is not given on the vacuum pump. If the volume of the vacuum container is made sufficiently large, furthermore, it becomes possible to carry out the vacuum evacuation in a manner that the lines are stabled. This purging method corresponds to the invention of claim 3. [Embodiment of the Invention] Now referring to the accompanying drawings, a preferred embodiment of the present invention will be described in detail. Fig. 1 shows one embodiment of the liquid supply unit according to the present invention. The illustrated liquid supply unit 20 serves to supply a liquid material for use in a film-forming process in a case of manufacturing semiconductor devices or liquid crystal panels to a film-forming unit (a point of use) as it is in a liquid phase. As liquid materials for a film-forming use, there are included various kinds of liquid materials such as titanium tetrachloride, TEOS, TMOP (trimethyl phosphate), TMP (trimethyl phsphite), TEB (triethyl borate), pentaethoxy tantalum and pentamethoxy tantalum, all of which are applicable in the present invention. The liquid supply unit 20 in a case where titanium tetrachloride is supplied to a gasification unit (not shown) in a CVD film-forming unit, will be described below.

The liquid supply unit 20 is connected for use with an exchangeable storage container 22 in which a liquid material, this is titanium tetrachloride, is stored. This storage container 22 is a small-sized cylindrical closed container whose volume is, for example, about 6 liters, and it is purchased for use as filled with a predetermined quantity of the liquid material. The storage container 22 has a first pipe 24 running through the ceiling plate portion of its container main body 23, in which the lower end thereof is positioned in the vicinity of its bottom and a second pipe 26 also running through the same ceiling plate portion, in which the lower end thereof terminates in its upper space. The upper end of said first pipe 24 functions as a liquid supply port 25 and the upper end of said second pipe 26 functions as a force-feeding gas intake port 27, and these pipes 24, 26 each has a shut-off valve 28, 30 provided thereon.

The liquid supply unit 20 comprises, similarly to the aforementioned construction of the prior art, a supplying line 34 connected with the liquid supply port 25 of said storage container 22 by a removable joint 32 and extending to a place of use and a force-feeding line 40 connected with the force-feeding gas intake port 27 of said storage container 22 by a removable joint 38 in order to supply a force-feeding gas such as helium gas from its supply source 36 to the inside of said storage container 22. The supplying line 34 has a valve 42 provided therein which is closed when the storage container is exchanged, and the force-feeding line 40 has a supply valve 44 provided therein for the force-feeding gas. As a purge system for purging the liquid material or gas in these lines 34, 40, there are provided a first purge gas line 48 for sending a purge gas such as nitrogen gas from its supply source 46 into the force-feeding line 40, a first discharging line 50 connected with the force-feeding line 40 to discharge the liquid material or gas in the lines 34, 40 to the atmosphere. The first discharging line 50 is connected with a vacuum evacuation apparatus whose reachable degree of vacuum is lower (e.g. about 50 Torr), preferably a gas ejector type vacuum generator 56 and a vacuum evacuation apparatus whose reachable degree of vacuum is higher (e.g, less than 1 Torr), preferably an oilless type vacuum pump 58, by way of branched lines 52, 54, respectively, and these vacuum evacuation apparatuses 56, 58 are designed to be selectively used by valves 60, 62, 64. Gas discharged from these vacuum evacuation apparatuses 56, 58 will be released to the atmosphere by way of a proper gas treatment unit (not shown).

Further, a bypath line 66 for communicating the supplying line 34 and the force-feeding line 40 with each other is disposed as nearly to the valves 28, 30 as possible. Between the valve 42 and joint 32 of the supplying line 34 and at a position near to the valve 42 is connected a second purge gas line 70 for sending a purge gas such as nitrogen gas from its supply source 68 into the supplying line 34. In addition, the lines 48, 50, 66, 70 each has a valve 72, 74, 75, 78 provided therein, and in particular, the valves 76, 78 are preferably attached on the side as near to the supplying line 34 as possible.

The aforementioned construction is substantially equal to the construction of the prior art shown in Fig. 3. A purge system of this embodiment is characterized in that the supplying line 34 and force-feeding line 40 each has further a valve 80, 82 attached at a position as near to their connection point 66 with the bypath line 66 as possible.

One end of a second discharging line 84 is connected with the connection point of the force-feeding line 40 and bypath line 66, and the other end thereof is connected with the first discharging line 50 and the branched line 54 on the side of the vacuum pump 58 by way of branched lines 86, 88, respectively. On the second discharging line 84, two valves 90, 92 and a vacuum container 94 are provided in order from the side of the force-feeding line 40. The branched lines 86, 88 each has a valve 96, 98 provided thereon. The vacuum container 94 has a volume enough larger than the total volume of a portion including the lines 34, 40, 66 to be vacuum- evacuated, preferably more than 1 ,000 cm3. A tape heater is further wound on places where the liquid material may pass, concretely on the lines, valves and vacuum container 94 surrounded by dotted lines 100, 102 in Fig. 1 , respectively. These tape heaters 100, 102 serve to heat the inside of the lines, vacuum container and the likes so that the gasification of the liquid material is accelerated. In addition, the tape heater 100 for the lines and valves and the tape heater 102 for the vacuum container 94 are separately connected with independent sources of electric power (not shown).

Furthermore, a line system represented by the reference numerals 104, 106 is connected with the purge gas supply source 46, and this line system serves to purge the inside of the vacuum container 94. In Fig. 1. in addition, a two-dot chain line 108 represents a cylinder cabinet. The reason why the constituent containers of the liquid supply unit 20 are surrounded by the cylinder cabinet 108 is intended to avoid such a situation that the liquid material is dispersed to the atmosphere even if it leaks out of the joint portions and valves of these lines because such liquid material to be handled has properties such as combustibility, combustion-supporting property, corrosivity and toxicity.

In the next place, a case where the storage container set in the. liquid supply unit 20 in the aforementioned construction has gotten empty and it must be exchanged with a new storage container fully filled with a liquid material, will be described here.

At first, it is confirmed that the valves 80, 82 get opened and the other valves are closed. Thereafter, an electric power is applied to the tape heater 100 so that the inside of the line 34 and the likes is heated to a temperature of 70 ^ 80 °C. By virtue of this heating, the gasification of titanium tetrachloride in a liquid phase existing in the line 34 and the likes is accelerated. At the same time, the valves 64, 98 are opened and the vacuum pump 58 is started up so that the insides of the vacuum container 94 is depressurized and evacuated to preferably less than 10 Torr. By opening thereafter the valves 74, 60 in the first discharging line 50 and the valves 28, 30 of the storage container 22, the liquid material in a liquid phase remaining in a part of the supplying line 34 and bypath line 66 is turned to the storage container 22 due to its own weight. After the passage of a predetermined period of time, the valves 28, 30 of the storage container 22 are closed, assuming that almost all the remaining liquid has been returned to the storage container 22.

Then, the valve 76 of the bypath line 66 is opened and the vacuum generator 56 is driven to vacuum-evacuate the inside of the lines 34, 40, 66, while keeping the open state of the valves 60, 70. After the inside of these lines has reached a predetermined degree of vacuum (about 50 Torr), the valves 60, 74 are closed and the driving of the vacuum generator 56 is stopped.

After it is confirmed that the degree of vacuum of the vacuum container 94 has reached a predetermined value (less than 10 Torr), the valve 98 between the vacuum container 94 and the vacuum pump 58 is closed. When the valves 90, 92 of the second discharging line 84 are thereafter opened, the insides of the supplying line 34, force-feeding line 40 and bypath line 66 are vacuum-evacuated. At this stage, in the prior art, the vacuum pump is directly connected witf) the lines and vacuum evacuation is carried out. In such a conventional method, however, a period of time required for the vacuum evacuation is considerably longer and the liquid material may adhere on the inner wall surface of the vacuum pump so that the performance thereof is lowered, where a desirable degree of vacuum can not be obtained. In a case where it is tried to carry out vacuum evacuation from the vacuum container 94 as in the present invention, on the contrary, the vacuum evacuation can be carried out for a very short period of time and in a stabled state because the volume of the vacuum container 94 is en'ough larger than the internal volume of the same lines. After the passage of a predetermined period of time, the valves 90, 92 are closed.

By driving the vacuum generator again and opening the valves 60, 70 and further opening the valve 78 of the second purge gas line 70, a small amount of the purge gas is caused to flow from the purge gas supply source 68. The valve 78 is preferably opened and closed in pulsation. By virtue of this operation, the gasified liquid material which remains in the supplying line 34 is discharged from the supplying line 34 by way of the bypath line 66, force-feeding line 40 and first discharging line 50.

At this point of time, liquid drops remaining in the line 34 and the likes are almost completely removed. In order to enhance the complete removal of liquid drops, furthermore, a cycle purge will be carried out several times. The cycle purge comprises repeating the vacuum evacuation by the vacuum generator 56 and the supply of the purge gas by way of the first purge gas line 48 or second purge gas line 70. This cycle purge will be satisfactorily carried out two or three times in this embodiment, although it has been carried out several times in the prior art. After the purge gas is finally filled in the line 34, all the valves are closed and at the same time the tape heater 100 is turned off, the storage container 22 is removed from the joint and exchanged with a new storage container.

In portions between the connection points of the supplying line 34 and force- feeding line 40 with the bypath line 66 and the valves 28, 30, a very small amount of gas may remain because it is apt to stagnate. It is therefore preferable to remove the storage container 22 from the joints 110, 112 positioned upperstream of the valves 80, 82 and to treat the bypath line 66 as one body united with the storage container 22 by a proper treatment installation. Judging from this point of view, it is effective to made the storage container 22 to be one including the bypath line 66 and the valves 80, 82 as its constituent elements and to change the liquid supply port and the force- feeding gas intake port to the positions of the joints 110, 112.

At a point of time when the exchanging work of the storage container 22 has been completed, the liquid material is contained in the gas phase and liquid phase states in the vacuum container 94. It is therefore necessary to purge the liquid material in the vacuum container 94. This purging work will be satisfactorily carried out at any time after the completion of the exchanging work of the storage container 22.

In the purging work of the vacuum container 94, at first, an electric power is supplied to the tape heater 102, thereby accelerating the gasification of the liquid material in a liquid phase in the vacuum container 94. Then, the valves 60, 96 are opened while opening the valves 92, 114 or the valve 116 to supply a small amount of purge gas, whereby the inside of the vacuum container 56 is vacuum- evacuated by the vacuum generator 56. Thereafter, a cycle purge is carried out by the opening and closing operation of the valves 114, 116, 60. Then, the valve 62 is opened and the inside of the vacuum container 94 is depressurized by the vacuum pump 58. At that time, the liquid material may be sent even in a small amount to the vacuum pump 57. However, there is no problem as to the lowering of the performance of the vacuum pump 58 caused by the liquid material during the driving of the vacuum pump 58 because all. the steps of the purging work of the vacuum container 94 can be carried out by remote operation and can be carried out at any time. If the vacuum evacuation by the vacuum pump 58 has been completed, the purge gas is filled into the vacuum container 94. Thereafter, the tape heater 102 is turned off and all the valves related with the vacuum container 94 are closed, thereby completing the purging work.

Although the preferred embodiment of the present invention has been described above in detail, it goes without saying that the present invention is not limited to the aforementioned embodiment.

For example, the line system for the purging work to be carried out on the exchange of the storage container 22 is not limited to that of the aforementioned embodiment. There can be conceived various types of line systems including one of having no second supplying line. Also as to the purging work, it is not limited to the procedure of the aforementioned embodiment.

As to the connection position of the vacuum container, in addition, there are also conceived various positions including the way of the first discharging line. [Effects of the Invention]

According to the present invention, as has been mentioned above, it becomes possible, in the purging work which is carried out on the exchange of the storage container, to carry out the vacuum evacuation of the lines satisfactorily and quickly, and further in a stabled state. The purging work and the exchanging work of the storage container can be therefore completed for a short period of time. Since the liquid material seldom remain in the lines, such a problem does not result that even if the lines are opened to the atmosphere on the exchange of the storage container, the liquid material remaining therein reacts to produce byproducts. Furthermore, since the sucked liquid material is temporarily stored in the vacuum container and is not sent to the vacuum evacuation apparatus such as the vacuum pump as it is, such a problem does not result that the performance of the vacuum evacuation apparatus is lowered during the purging work. [Brief Description of the Drawings]

Fig. 1 is a schematic illustrative view showing one embodiment of the liquid supply unit according to the present invention;

Fig. 2 is a schematic illustrative view showing a liquid supply unit of the prior art; and Fig. 3 is a schematic illustrative view showing a liquid supply unit of the prior art. [Description of Reference Numerals]

20 -- liquid supply unit,

22 --exchangeable storage container, 25 - liquid supply port,

27 -- force-feeding gas intake port,

34 - supplying line,

40 - force-feeding line,

48 - first purge gas line (purge gas supply means), 50 - first discharging line (vacuum evacuation means),

56 - vacuum generator (vacuum evacuation means),

58 - vacuum pump (vacuum evacuation means),

66 - bypath line,

70 - second purge gas line (purge gas supply means), 94 - vacuum container (vacuum evacuation means).

Claims

1. A liquid supply unit for supplying a liquid material stored in an exchangeable storage container to a place of use, which comprises: a supplying line detachably connected with a liquid supply port of said storage container for supplying the liquid material in said storage container to the place of use; a force-feeding line detachably connected with a force-feeding gas intake port of said storage container for introducing a force-feeding gas into said storage container so that the liquid material is forcibly fed through said supplying line; a bypath line for communicating said supplying line and said force-feeding line with each other; a purge gas supply means for supplying a purge gas to said supplying line; and a vacuum evacuation means for vacuum-evacuating the inside of said supplying line, wherein said vacuum evacuation means has a vacuum container constructed such that its inside is depressurized to a predetermined degree of vacuum, and connected with said force-feeding line.

2. A liquid supply unit according to claim 1 , in which said bypath line is made capable of being detached from said supplying line and said force-feeding line as one united body with said storage container.

3. A purging method in a liquid supply unit for supplying a liquid material stored in an exchangeable storage container to a place of use, which comprises a supplying line detachably connected with a liquid supply port of said storage container for supplying the liquid material in said storage container to the place of use, a force- feeding line detachably connected with a force-feeding gas intake port of said storage container for introducing a force-feeding gas into said storage container so that the liquid material is forcibly fed through said supplying line and a bypath line for communicating said supplying line and said force-feeding line with each other, said method being carried out in a case where said storage container is exchanged, which method comprises: a first step of providing a vacuum container and depressurizing the inside of said vacuum container to a predetermined degree of vacuum; and a second step of connecting said vacuum container which has been depressurized in the first step with said force-feeding line, and vacuum-evacuating the inside of said supplying line by way of said bypath line.