Patent Application
20050260081
This application is based upon and claims the benefit of priority from prior Japanese Patent Application 2001-263533 filed on Aug. 31, 2001; the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to a vacuum pumping system, which is used in general industry or in a semiconductor manufacturing equipment. In particular, it is related to a vacuum pumping system, which provides improved longevity through failure prevention thereof.
2. Description of the Related Art
Problems of the conventional vacuum pumping system often utilized in general industry or in many semiconductor manufacturing equipments will be described. As an example, problems relating to the vacuum pumping system, which is used in a low-pressure chemical vapor deposition (LPCVD) equipment, specifically a tandem pump system, which is used in a LPCVD equipment for a silicon nitride film (Si3N4 film), will be described.
Conventionally, deposition of a silicon nitride film through a LPCVD method involves the chemical reaction of dichlorosilane (SiH2Cl2) gas, which is used as a silicon source, and ammonia (NH3) gas, which is used as a nitride species, under low pressure conditions at approximately 800° C. to deposit a silicon nitride film upon a silicon (Si) substrate. In addition to generating the silicon nitride, the chemical reaction produces the reaction by-products of ammonium chloride (NH4Cl) gas and hydrogen (H2) gas. The hydrogen in gas phase is evacuated through the vacuum pumping system utilizing the LPCVD equipment. On the other hand, since the temperature within the reactor is approximately 800° C. and it is under low pressure conditions of several 100 Pa or less at the time of formation, the ammonium chloride is also in the gas phase. The LPCVD equipment typically has a trap for collecting solid phase by-products, disposed between a LPCVD chamber and the vacuum pumping system.
However, it is impossible to completely collect the solid phase by-products with the trap since pressure at the location of the trap is low. Accordingly, the ammonium chloride that has not been collected reaches the vacuum pumping system. The vacuum pumping system generates an approximately five digits difference in pressure before and after the evacuation pump, where there is approximately 0.1 Pa of pressure on the upstream side and atmospheric pressure on the downstream side under such operational performance. While the ammonium chloride is in a gas phase at the time of formation, it begins to solidify within the evacuation pump as the pressure increases due to gas compression therein. At the portions where solidification has begun, exhaust conductance decreases due to reduction of the pipe radius, and solidification is further accelerated there. In other words, localized solidification that has begun in one portion rapidly accelerates, and the pipes ultimately are blocked, or adhesion to the rotating portions happens making rotation impossible, thereby making the vacuum pumping system fail. Failure of the vacuum pumping system maybe caused by catastrophic failure in just one portion, resulting in an vacuum pumping system with a remarkably short life span.
A first aspect of the present invention inheres in a vacuum pumping system including: an evacuation conduit, having a sequence of monitoring zones serially assigned in an exhaust direction; sensors respectively provided to the monitoring zones and independently detecting the conditions of the monitoring zones; heaters respectively provided to the monitoring zones and being paired with the sensors; and a control unit receiving data signals from the sensors, comparing the data signals with a threshold value, and when the data signals from a specific sensor exceed the threshold value, selectively supplying heating power to a heater of the monitoring zone where the specific sensor is provided.
A second aspect of the present invention inheres in a vacuum pumping system, being connected such that a group of evacuation elements regulate a fixed evacuation direction, including: a specific evacuation element included among the group of the evacuation elements; a first valve connected to a suction side piping of the specific evacuation element; a branching vacuum piping, having an exhaust side piping connected to the first valve; a second valve connected to other exhaust side piping of the branching vacuum piping; a bypass piping having a suction side piping connected to the second valve; other evacuation elements connecting one of the suction side piping to an exhaust side piping of the specific evacuation element, and the other suction side piping to an exhaust side piping of the bypass piping; sensors connected to at least one of the suction side piping of the specific evacuation element, the exhaust side piping of the specific evacuation element, and a main body of the specific evacuation element; and a control unit receiving data signals from the sensors, comparing the data signals with a threshold value, and when the data signals exceed the threshold value, respectively supplying signals for closing the first valve and opening the second valve to the first and second valves.
A third aspect of the present invention inheres in a method for monitoring an evacuation conduit including: evacuating a reactive gas and a reaction by-product of the reactive gas by the evacuation conduit having a plurality of monitoring zones serially arranged in an evacuation direction; independently detecting respective conditions of the monitoring zones by sensors provided respectively to the monitoring zones; receiving respective data signals from the sensors; comparing the data signals with a threshold value; and selectively supplying heating power to only a heater of the monitoring zone where the specified sensor is arranged, when the data signals from a specific sensor exceeds the threshold value.
A fourth aspect of the present invention inheres in a method for monitoring an evacuation conduit including: evacuating a reactive gas and a reaction by-product of the reactive gas, by the evacuation conduit, including a first valve connected to a suction side piping of a specific evacuation element, a branching vacuum piping having an exhaust side piping connected to the first valve, a second valve connected to other exhaust side piping of the branching vacuum piping, a bypass piping having a suction side piping connected to the second valve; detecting a condition of the specific evacuation element by sensors connected to at least one of the suction side piping of the specific evacuation element, the exhaust side piping of the specific evacuation element, and the main body of the specific evacuation element; and receiving data signals from the sensors, comparing the data signals with a threshold value, and when the data signals from a specific sensor exceeds the threshold value, supplying respectively signals for closing the first valve and opening the second valve to the first and second valves.
Various embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the same or similar reference numerals are applied to the same or similar parts and elements throughout the drawings, and the description of the same or similar parts and elements will be omitted or simplified.
As shown in
More specifically, in the vacuum pumping system according to the first embodiment of the present invention, the evacuation conduit 2 has a large variety of and a plurality of sensors 101, 102, 103, . . . , 104, which constantly monitor its condition, mounted thereon. The group of a large variety and a plurality of sensors 101, 102, 103, . . . , 104 constantly sends to the control unit 1 the condition of the evacuation conduit 2. Temperature gauges, pressure gauges, flowmeters, ammeters/voltmeters or vibration gauges may be considered as the sensors 101, 102, 103, . . . , 104. A comparator, which compares the received data signals D1, D2, D3, . . . , Dm with the threshold value, is provided within the control unit 1. Analog comparison with the threshold value may be made, or alternatively, comparison may be made with a digital circuit.
In the case of comparing with a digital circuit, information from the group of the sensors 101, 102, 103, . . . , 104 passes through an A/D converter, which is provided to the output circuit of the sensors 101, 102, 103, . . . , 104, and is concentrated in the control unit 1 as digital signals. Otherwise, it may be structured such that they are transmitted to the control unit 1 as analog signals, passed through an installed A/D converter of an input circuit of the control unit 1, so as to be input into the comparator after being transformed into digital signals. Employing either method, the information D1, D2, D3 . . . , Dm from the group of the sensors 101, 102, 103, . . . , 104 is collected by the control unit 1. For performing further detailed diagnosis/analysis of the information D1, D2, D3, . . . , Dm, a central processing unit (CPU) may be installed. The CPU is controlled in conformity with predetermined software.
In this manner, the control unit 1 diagnoses/analyzes the information D1, D2, D3, . . . , Dm from the group of sensors 101, 102, 103, . . . , 104, and controls the group of the heaters 201, 202, 203, . . . , 204 based on the results.
In
During the LPCVD method for the silicon nitride film using dichlorosilane (SiH2Cl2) and ammonia (NH3) as source gases, ammonium chloride (NH4Cl) gas, a reaction by-product, is generated as a result. Normally, a trap, which collects these unreacted source gases (reactive gases) and the reaction by-product (NH4Cl) from the reaction of the source gases, is inserted between the evacuation conduit 2 and the CVD reactor (chamber) in the LPCVD equipment. It is impossible for the trap to completely collect the reaction by-product due to low pressure. The reaction by-product that is not collected reaches the evacuation conduit 2. The pressure in the evacuation conduit 2, which has the plurality of evacuation elements 21, . . . , 24, 25, 26, 27, increases from approximately 0.1 Pa to normal atmospheric pressure due to the compression of the gas. The reaction by-product exists as a gas under low pressure conditions; it begins to solidify in accordance with the sublimation curve of the phase diagram as the pressure increases. Within the pump, since the pressure changes from several hundred Pa to the normal atmospheric pressure through repeated compression of the gas, the gaseous reaction by-product within the exhaust gas begins to solidify in the evacuation conduit 2 as the pressure increases. If the solidification begins in the piping of the evacuation conduit 2, the volume of the piping or the gas coolers 25, 27 decreases, and the exhaust conductance decreases. The pressure further increases in the portions of the reaction by-product solidifying/adsorbing, whereby as a result, the temperature begins to rise.
In the control unit 1, the threshold values (permissible values) are set so as to permit the temperature to rise up to approximately a certain degree Celsius in each of the plurality of monitoring zones of the evacuation conduit 2. The threshold values are determined based upon control information, which takes into account the starting condition of the LPCVD equipment and the operating status of the evacuation conduit 2 accumulated up to the present. In the first embodiment, the temperature rise threshold value is set to “a rise of 10° C. from the initial condition”. When the rise in temperature reaches the threshold value, the control unit 1 supplies power to only the heater on the corresponding monitoring zone in the heaters 211, 212, . . . , 221, 222, 223, 224, 225, 226, 227, 228, 229, which are attached inside the plurality of monitoring zones of the evacuation conduit 2, selectively raising the temperature of only the corresponding monitoring zone.
For example, it is assumed that clogging at the piping 35 on the suction side of the first stage gas cooler 25 disposed in upstream begins due to adhesion of the reaction by-product, and a rise in temperature occurs. As previously mentioned, there are three stages of gas coolers in all. In this case, the heater 223 for the piping 35 on the suction side of the first stage gas cooler 25, the heater 225 for the piping 38 on the exhaust side and the heater 224 for the outer wall portion of the first stage gas cooler 25 are heated to 180° C. The preset temperature of the heaters 223, 225, 224 is the temperature at which ammonium chloride sublimes. Accordingly, since a reaction by-product generated by a LPCVD equipment of other material has different properties, the LPCVD equipment for the other material requires setting a temperature corresponding to the reaction by-product. By raising the temperature of the heaters 223, 225 and 224, adhesion of the reaction by-product at the first stage gas cooler 25 stops progressing any further.
By continuing to perform a semiconductor manufacturing process, adhesion and clogging in other monitoring zones progresses and thus changes arise in the condition of the evacuation conduit 2. Similar to the aforementioned processing, the control unit 1 raises the temperature of the corresponding heater in the heaters 211, 212, . . . , 221, 222, 223, 224, 225, 226, 227, 228, 229 to 180° C. when the change in the evacuation conduit 2 condition exceeds the threshold value, which is set for a newly clogged monitoring zone. Successively, dispersing the solidified/adsorbed reaction by-product is possible by repeating the same process (operation).
Conventionally, solidification drastically accelerates in the portions where the reaction by-product has begun to adhere, becoming a catastrophic failure that makes the pump fail. However, according to the first embodiment, it is possible to suppress further adhesion in the portion where clogging has begun, dispersing the reaction by-product to other monitoring zones. Thus, the life span of the LPCVD equipment may be lengthened.
In the first embodiment, a method for suppressing adhesion of a reaction by-product, which is generated in a portion of the monitoring zones of the evacuation pump system, by heating specific monitoring zones Z1, Z2, Z3, . . . , Zm, however, other methods are also possible.
Here, sensors 122, 123, 124 are provided to the suction side piping 37 of the first stage first stage gas cooler 25, the main frame of the first stage gas cooler 25, and the exhaust side piping 28 of the first stage gas cooler 25. As with the first embodiment, the second embodiment is described with temperature gauges as the sensors. The control unit 1 receives data signals from these sensors 122, 123, 124, compares the data signals with the threshold value, and when these data signals exceed the threshold value, respectively supplies to the first valve 50 and second valve 51 signals for closing the first valve 50 and opening the second valve 51. Consequently, the sensors 122, 123, 124 and the control unit 1 are connected to each other by the wiring 322, 323 and 324. Furthermore, the first valve 50 and second valve 51 are connected to the control unit 1 via respective wiring 450 and 451. In order to open and close the first valve 50 and second valve 51 in conformity with electrical signals from the control unit 1, the first valve 50 and second valve 51 may be magnetic valves or pneumatic valves which operate by air pressure. In the case of the pneumatic valves, the air pressure respectively supplied to the first valve 50 and second valve 51 may be controlled by a pneumatic piping system, which is connected to the first valve 50 and second valve 51. More specifically, the first valve 50 and second valve 51 may be controlled to open and close by driving the magnetic valves, which control the pneumatic piping system, in conformity with electrical signals from the control unit 1.
In this manner, the method depending on the provision of the bypass piping 36 may also allow for lengthening of the evacuation conduit 2 life span. In the initial condition where clogging has not occurred, the first valve 50 is in an open status and the second valve 51 is in a closed status. In other words, gas passes through the first stage gas cooler 25. In the LPCVD equipment for Si3N4 films, the upstream side first stage gas cooler 25 often clogs up. If the rise in temperature due to clogging exceeds the threshold value, the control unit 1 closes the first valve 50 and simultaneously opens the second valve 51. The exhaust gas passes through the bypass piping 36 and flows into the fourth stage main pump 26. Namely, if it is conventional, when clogging of the first stage gas cooler 25 occurs, replacement of the entire evacuation conduit 2 is necessary; however, by allowing operation of the portions where clogging has not occurred using the bypass piping 36, lengthening the evacuation conduit 2 life span becomes possible.
It should be noted that the evacuation elements other than the first stage gas cooler 25, such as the backing pump (mechanical booster pump) 21, the first stage main pump (omitted from the drawing), the second stage main pump (omitted from the drawing), the third stage main pump 24, the fourth stage main pump 26, the second stage gas cooler 27, the fifth stage main pump (omitted from the drawing), and the third stage gas cooler (omitted from the drawing), may also be provided automatic valves for switching to the bypass piping.
The present invention has been described through the first and second embodiments as mentioned above, however the descriptions and drawings that constitute a portion of this disclosure should not be perceived as limiting this invention. Various modified examples of the embodiments, alternative embodiments, working examples and operational techniques will become clear to persons skilled in the art from this disclosure.
For example, the structure may have other evacuation elements further arranged on the bypass piping 36 side of
Similar to
As shown in
As such, by making the first stage gas cooler 25 and the spare gas cooler 28 be symmetrically formed, when clogging occurs in one, it may be switched over to the other, and the gas cooler where clogging occurred may be overhauled. Accordingly, with the evacuation conduit 2 in an operating state, the clogging may be resolved, allowing for the further lengthening of the evacuation conduit 2 life span.
It should be noted that the evacuation elements other than the first stage gas cooler 25, such as the backing pump (mechanical booster pump) 21, the first stage main pump (omitted from the drawing), the second stage main pump (omitted from the drawing), the third stage main pump 24, the fourth stage main pump 26, the second stage gas cooler 27, the fifth stage main pump (omitted from the drawing), and the third stage gas cooler (omitted from the drawing), may also be formed with symmetrical structures.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof. Accordingly, the present invention naturally includes various embodiments not specifically mentioned herein. Therefore, the technical scope of the present invention may be limited only by the scope of the patent claims deemed reasonable from the above description.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2001-263533 | Aug 2001 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10224255 | Aug 2002 | US |
| Child | 11190941 | Jul 2005 | US |
