EP3485168B1 - Method for lowering the pressure in a loading and unloading lock and associated pumping unit - Google Patents
Method for lowering the pressure in a loading and unloading lock and associated pumping unit Download PDFInfo
- Publication number
- EP3485168B1 EP3485168B1 EP17735085.7A EP17735085A EP3485168B1 EP 3485168 B1 EP3485168 B1 EP 3485168B1 EP 17735085 A EP17735085 A EP 17735085A EP 3485168 B1 EP3485168 B1 EP 3485168B1
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- EP
- European Patent Office
- Prior art keywords
- vacuum pump
- pressure
- pump
- rough
- secondary vacuum
- Prior art date
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- 238000005086 pumping Methods 0.000 title claims description 69
- 238000000034 method Methods 0.000 title claims description 20
- 239000007789 gas Substances 0.000 claims description 32
- 239000000758 substrate Substances 0.000 claims description 21
- 238000011144 upstream manufacturing Methods 0.000 claims description 7
- 230000006835 compression Effects 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 238000013021 overheating Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 210000000078 claw Anatomy 0.000 description 1
- 238000004320 controlled atmosphere Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
- F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
- F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
- F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
- F04C18/126—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/02—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for several pumps connected in series or in parallel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/08—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the rotational speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C2210/00—Fluid
- F04C2210/22—Fluid gaseous, i.e. compressible
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C2220/00—Application
- F04C2220/30—Use in a chemical vapor deposition [CVD] process or in a similar process
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C2270/00—Control; Monitoring or safety arrangements
- F04C2270/20—Flow
- F04C2270/205—Controlled or regulated
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2210/00—Working fluid
- F05B2210/10—Kind or type
- F05B2210/12—Kind or type gaseous, i.e. compressible
Definitions
- the present invention relates to a method of lowering pressure in a lock loading and unloading (or "load-lock" in English) of a substrate, such as a flat screen display ("or flat panel display” in English) or a photovoltaic substrate, from atmospheric pressure to low pressure for loading and unloading the substrate in a treatment chamber maintained at low pressure.
- a substrate such as a flat screen display ("or flat panel display” in English) or a photovoltaic substrate
- the present invention also relates to an associated pumping group for the implementation of said pressure lowering method.
- EP 1,746,287 A1 which recommends choosing a ratio of the respective nominal flow rates of the secondary and primary pumps from 10 to 15.
- an important step consists in treating a substrate under a controlled atmosphere at very low pressure in a process chamber.
- the atmosphere surrounding the substrate is first lowered at low pressure by a loading and unloading lock communicating with the process chamber.
- the airlock includes a sealed enclosure, a first door of which communicates the interior of the enclosure with an area under atmospheric pressure, such as a clean room, for loading at least one substrate.
- the airlock enclosure is connected to a pumping unit allowing the pressure in the enclosure to be lowered until an appropriate low pressure similar to that prevailing in the process chamber is reached so as to be able to transfer the substrate to the process chamber .
- the airlock also has a second door for discharging the substrate into the process chamber after being placed under vacuum. This same airlock is generally also used for the pressure rise of the substrate after its treatment, and its unloading at atmospheric pressure.
- each loading or unloading of substrates requires lowering and then alternately raising the pressure in the airlock enclosure, which implies the frequent intervention of the pumping group. It is also understood that the establishment of the vacuum in the airlock enclosure is not instantaneous and that this constitutes a limit to the overall speed of the manufacturing process. This limit is all the more sensitive when the substrates are large. This is particularly the case, for the manufacture of flat display screens or photovoltaic substrates, the enclosure of the airlock necessarily having the appropriate volume to contain one or more flat screens. For example, currently, the chambers of airlocks used for the manufacture of flat screens have large volumes, generally of the order of 500 to 1000 liters, and sometimes exceeding 5000 liters, which must therefore be pumped as quickly as possible.
- Particularly powerful pumping groups are used for this, in particular for ensuring pumping at the opening of the airlock, when the pressure in the enclosure is at atmospheric pressure.
- the pumping unit comprises one or more primary vacuum pumps and a secondary vacuum pump, such as a single-stage vacuum pump of the Roots type.
- the secondary vacuum pump is arranged upstream of the primary pump in the direction of flow of the gases to be pumped. Its main purpose is to “boost” the overall pumping speed of the low pressure pumping group.
- the flow generated by the secondary vacuum pump can be of the order of five times the flow generated by the primary pump. Due to the strong gas flow at the opening of the airlock, a significant pressure is generated at the discharge of the secondary vacuum pump, which can reach up to 4 bar (or 3 bar relative). This high overpressure causes a very high consumption of the secondary vacuum pump and a congestion at the suction of the primary vacuum pump, constituting a risk of malfunction for both the primary vacuum pump and for the secondary vacuum pump.
- a known solution consists in arranging a pipe connecting the inlet of the primary vacuum pump to the inlet of the secondary vacuum pump.
- the pipeline is fitted with a recirculation valve (or “bypass” in English), calibrated to open when the pressure difference between the suction and the discharge of the secondary vacuum pump becomes too large, generally tared for s '' open for a maximum pressure difference between 50 and 80 mbar.
- the recirculation valve opens at the start of the pressure drop, to circulate the excess gas flow from the discharge to the suction of the secondary vacuum pump.
- the recirculation valve closes.
- the pressure drop is therefore only ensured by the primary vacuum pump, the role of the secondary vacuum pump is then only to participate in the "recirculation" of the gas flow.
- the recirculation valve thus protects the primary vacuum pump by diverting the excess gas flow. This recirculation also thermally protects the secondary vacuum pump by preventing its discharge pressure from becoming too high.
- the drop in pressure in the airlock then generates the pressure reduction on the discharge of the secondary vacuum pump and the closing of the recirculation valve, thus allowing the secondary vacuum pump to start compressing the gases to be pumped from a pressure in the airlock generally of the order of 200 mbar.
- the initial overall pumping speed of the pumping unit is low because pumping is only ensured by the primary vacuum pump.
- the recirculation valve operates in a pulsating manner, opening and closing cyclically very quickly, in particular due to the principle of cyclic pumping of the volumetric secondary vacuum pump. This may result in the risks of premature mechanical wear of the recirculation valve and therefore the risk of leaks. Also, the pulsating operation of the recirculation valve can be the source of noise.
- the gases which circulate in the pipe of the recirculation valve are hot, due to the compression of the secondary vacuum pump. These recycled hot gases can also contribute to the heating of the secondary vacuum pump.
- One of the aims of the present invention is therefore to propose a process for lowering pressure in a loading and unloading airlock and an associated pumping unit which at least partially solve the problems of the state of the art, by allowing in particular increase the pumping speed at the start of the pressure drop while reducing the power consumed by the secondary vacuum pump.
- Another object of the present invention is to protect the primary vacuum pump and the secondary vacuum pump from the risks of damage linked to the excess gas flow when the airlock is opened at atmospheric pressure.
- Another object of the present invention is to limit the risks of wear of the recirculation valve and the heating of the secondary vacuum pump by the “recycled” hot gases.
- the subject of the invention is a process for lowering pressure in an airlock for loading and unloading a substrate at atmospheric pressure by a pumping group comprising a primary vacuum pump and a secondary vacuum pump arranged in upstream of said primary vacuum pump in the direction of flow of the gases to be pumped, characterized in that during the pressure drop and until the pressure in the loading and unloading lock reaches a threshold of predefined low pressure, the rotation speed of the secondary vacuum pump is controlled according to an operating parameter of the secondary vacuum pump to increase the flow generated by the secondary vacuum pump so that the flow generated by the pump with no-load secondary is included in a range whose high value corresponds to six times the flow generated by the primary vacuum pump and the low value at 1.3 times the flow generated by the primary vacuum pump.
- the invention also relates to a pumping unit comprising a primary vacuum pump and a secondary vacuum pump, said secondary vacuum pump being arranged upstream of said primary vacuum pump in the direction of flow of the gases to be pumped and comprising a frequency converter, characterized in that the secondary vacuum pump comprises a control unit connected to the frequency converter, configured to control the speed of rotation of the secondary vacuum pump as a function of a signal representative of a parameter of the secondary vacuum pump, so that during the pressure drop and until the pressure in the loading and unloading airlock reaches a predefined low pressure threshold, the flow generated by the pump secondary vacuum is increased and included in a range whose high value corresponds to six times the flow generated by the primary vacuum pump and the low value, to 1.3 times the flow generated by the primary vacuum pump.
- the primary vacuum pump comprises a load shedding module of a pumping stage.
- the signal representative of an operating parameter of the secondary vacuum pump is for example a parameter of the motor of the secondary vacuum pump, such as the current or the power.
- the pumping unit comprises a recirculation line connecting the inlet of the primary vacuum pump to the inlet of the secondary vacuum pump, the recirculation line comprising a discharge module configured to open as soon as the suction pressure of the primary vacuum pump exceeds the suction pressure of the secondary vacuum pump by a predefined overshoot value between 100 and 400 mbar.
- the secondary vacuum pump is for example a ROOTS type vacuum pump.
- the ratio of the flow rates generated between the primary vacuum pump and the secondary vacuum pump is adapted so that it is optimal. More precisely, a flow generated by the secondary vacuum pump admissible for the high initial gas flow is maintained, that is to say less than six times the flow generated by the primary vacuum pump. Simultaneously, an optimized generated flow is maintained for the primary vacuum pump, that is to say greater than 1.3 times the flow generated by the primary vacuum pump to ensure gas compression as soon as possible.
- the pressure difference between the suction and the discharge of the secondary vacuum pump then remains less than a value between 150 and 300 mbar.
- the pipe and the recirculation valve of the device of the prior art, calibrated to open for a pressure differential of the secondary vacuum pump of between 50 and 80 mbar, can then be eliminated.
- the pumping unit can however include a discharge module configured to open as soon as the pressure difference between the suction and the discharge of the secondary vacuum pump exceeds a higher value, between 100 and 400 mbar , according to the value of the flow rate ratio which is selected and according to the mechanical safety settings, making it possible to protect the vacuum pumps in particular while the speed control is effective.
- the secondary vacuum pump As soon as the rotation speed of the secondary vacuum pump is controlled, the secondary vacuum pump is no longer "short-circuited", as it was above a pressure of 200mbar in the airlock of the state of the art, but it is used as if it were the real first pumping stage of the primary vacuum pump.
- the operating characteristics of the secondary vacuum pump are thus adapted to the capacities of the primary vacuum pump so that the secondary vacuum pump can be effective almost from atmospheric pressure. This results in a significant drop in the power consumed as well as an increase in the overall pumping speed of the pumping unit at the start of the pressure drop, and therefore, a reduction in the pressure drop time in the airlock.
- the pumping speed increases from 20 to 50%, compared to the pumping speed of the devices of the prior art.
- the overall time of pressure drop in the enclosure of a 500-liter airlock between a pressure close to 1000 mbar at a transfer pressure of the order of 0.1 mbar goes from 25 to 20 seconds, i.e. a reduction of around 20%.
- the discharge module opens at a higher pressure than the prior art recirculation valve and, subsequently, the flow ratio between the primary and secondary vacuum pumps is optimized, the discharge pressure of the secondary vacuum pump decreases rapidly so that the discharge module is only open for a very short time. Being little used, the discharge module wears less quickly and is less noisy. In addition, little gas circulates in the recirculation line, which prevents overheating of the secondary vacuum pump by hot compressed gases.
- atmospheric pressure the surrounding pressure outside the airlock for loading and unloading of the substrate, such as the pressure prevailing in a room in which clean room operators work, that is to say a pressure of the order of 10 5 Pascal (1000 mbar) or slightly higher to favor the direction of flow towards the outside of the enclosure.
- the figure 1 shows an example of a pumping unit 1 intended to be connected to a loading and unloading airlock enclosure (or "load lock” in English) via an isolation valve (not shown).
- the loading and unloading airlock comprises a sealed enclosure, a first door of which communicates the interior of the enclosure with an area under atmospheric pressure, such as a clean room, for loading at least one large-volume substrate, such as a flat panel display or a photovoltaic substrate.
- Such airlocks have a volume generally between 500 and 5000 liters.
- the airlock also includes a second door for discharging the substrate into the process chamber after vacuum, as well as a device for introducing a neutral gas, in particular for returning to atmospheric pressure after treatment of the substrate.
- the pumping unit 1 comprises a primary vacuum pump 2 and a secondary vacuum pump 3 arranged upstream of the primary vacuum pump 2 in the direction of flow of the gases to be pumped.
- the primary vacuum pump 2 comprises for example a multi-stage dry vacuum pump, with rotary lobes such as of the Roots type with two or three lobes (bi-lobes, tri-lobes). According to other embodiments not described, the primary vacuum pump comprises several pumps in series or in parallel. In addition, other conventional pumping principles can be used for the primary vacuum pump.
- the primary vacuum pump 2 shown diagrammatically on the figure 1 comprises for example five pumping stages T1, T2, T3, T4, T5, connected in series one after the other with a generated flow decreasing with the position of the pumping stage in the series, and between which a gas to be pumped between an inlet 4 and an outlet 5.
- a "Roots" rotary lobe vacuum pump comprises two rotors of identical profiles, carried by two shafts extending in the pumping stages T1, T2, T3, T4, T5 and driven by a pump motor.
- primary vacuum 2 (not shown) to rotate inside a stator in the opposite direction.
- the sucked gas is trapped in the free space between the rotors and the stator, then it is pushed back.
- the operation is carried out without any mechanical contact between the rotors and the stator of the primary vacuum pump 2, which allows the total absence of oil in the pumping stages T1, T2, T3, T4, T5.
- the first pumping stage T1 of the primary vacuum pump 2 has a generated flow rate So1 of the order of 600 m 3 / h
- the second pumping stage T2 has a generated flow rate So2 of the order of 400m 3 / h
- the third pumping stage T3 has a generated flow So3 of the order of 200m 3 / h
- the last two pumping stages T4 and T5 have a generated flow So4, So5 of the order of 100m 3 / h.
- the flow rates generated varying as a function of the pressure range, these values correspond to the maximum values, at constant pumping flow, with a speed of rotation of the primary vacuum pump 2 in fixed operation and of the order of 65 Hz.
- the primary vacuum pump 2 also comprises a non-return valve 6 at the outlet of the last pumping stage T5, at the level of the discharge 5, to prevent the return of the gases pumped into the primary vacuum pump 2.
- the secondary vacuum pump 3 is, like the primary vacuum pump 2, a volumetric vacuum pump, that is to say a vacuum pump which, using pistons, rotors, vanes, valves, sucks, transfers and then expels the gas to be pumped.
- the secondary vacuum pump 3 is for example a single-stage vacuum pump (having only one pumping stage), with rotors such as the Roots type or of a similar principle, such as the Claw type.
- the maximum flow generated SoR of the secondary vacuum pump 3 is for example of the order of 3000 m 3 / h at maximum rotation speed (ie at about 70 Hz), in the optimal pressure range.
- the secondary vacuum pump 3 comprises a motor 7, such as an asynchronous motor, a frequency converter 8 for controlling the motor 7 driving the rotors and a control unit 9 connected to the frequency converter 8.
- a motor 7 such as an asynchronous motor
- a frequency converter 8 for controlling the motor 7 driving the rotors
- a control unit 9 connected to the frequency converter 8.
- control unit 9 is configured to control the speed of rotation of the rotors of the secondary vacuum pump 3 as a function of a signal representative of an operating parameter of the secondary vacuum pump 3 to increase the flow generated so that the flow generated by the secondary vacuum pump SoR is understood in a range whose high value corresponds to six times the flow generated by the Sol primary vacuum pump and the low value at 1.3 times the flow generated by the Sol primary vacuum pump.
- the predefined low pressure threshold is for example 20 mbar. Below this, the speed of rotation of the secondary vacuum pump 3 is controlled to its maximum value, that is to say 70 Hz in the present example.
- the pressure difference between the suction and the discharge of the secondary vacuum pump then remains less than a value between 150 and 300 mbar.
- the signal representative of an operating parameter is for example the discharge pressure of the secondary vacuum pump P1 or a parameter of the motor 7 of the secondary vacuum pump 3.
- the parameter of the motor 7 of the secondary vacuum pump 3 can be the current, representative of the power consumed, or directly the power consumed. These signals can be received from the variable speed drive 8 connected to the motor 7.
- the control of the secondary vacuum pump 3 is autonomous since it requires neither information from the loading and unloading lock, nor addition of pressure sensor to the inlet inlet 4 of the primary vacuum pump 2.
- the control of the rotational speed of the rotors of the secondary vacuum pump 3 as a function of a signal representative of an operating parameter of the secondary vacuum pump 3 is a closed loop control: when the discharge pressure P1 or the motor current 7 or the power increases and the generated flow approaches or exceeds the high value of the authorized range, the speed of rotation is slowed down, even decreased.
- the pumping unit 1 also comprises a pipe 10 connecting the inlet 4 of the primary vacuum pump 2 to the inlet inlet 11 of the secondary vacuum pump 3.
- the pipe 10 includes a discharge module, such as a valve 12 or a valve controlled by the treatment unit 9, configured to open as soon as the pressure difference between the suction and the discharge of the secondary vacuum pump 3 exceeds a predefined overshoot value ⁇ P, between 100 and 400 mbar, the overshoot value ⁇ P being defined according to the ratio of the generated flows retained and according to the mechanical safety settings.
- a discharge module such as a valve 12 or a valve controlled by the treatment unit 9 configured to open as soon as the pressure difference between the suction and the discharge of the secondary vacuum pump 3 exceeds a predefined overshoot value ⁇ P, between 100 and 400 mbar, the overshoot value ⁇ P being defined according to the ratio of the generated flows retained and according to the mechanical safety settings.
- the pressure difference of the secondary vacuum pump 3 is always less than a pressure of the order of 250 mbar.
- the discharge module is therefore configured to open as soon as the suction pressure of the primary vacuum pump P1 exceeds the suction pressure of the secondary vacuum pump Pasp by an overshoot value ⁇ P predefined for example at 300mbar .
- the primary vacuum pump 2 is designed to be able to absorb and transfer this strong gas flow with the power consumed. as low as possible.
- the primary vacuum pump 2 includes a load shedding module of a pumping stage.
- the flow generated from the secondary vacuum pump SoR is adapted to correspond to the flow generated from the primary vacuum pump Sol, that is to say the flow generated by the first pumping stage T1 of the pump primary vacuum 2, the second or third pumping stage T2, T3 can in turn limit the overall generated flow rate of the primary vacuum pump 2.
- the primary vacuum pump 2 can punctually absorb flows of significant pumping corresponding in this example to a suction pressure P1 limited to the opening pressure of the discharge module, that is to say 300 mbar
- the load shedding module is connected to the output of a pumping stage low pressure, such as the second pumping stage T2.
- the load-shedding module comprises for example a channel 13 connecting the output of the low pressure stage (T1 or T2) to the discharge 5 of the primary vacuum pump 2.
- the channel 13 is provided with a valve 14.
- the rotation speed of the secondary vacuum pump 3 is at a reduced fixed rotation speed, for example of the order of 30 Hz in order to limit the electrical consumption.
- the lock opens the isolation valve isolating the enclosure at atmospheric pressure from the pumping unit 1 (tl).
- the secondary vacuum pump 3 compresses the excess gas coming from the enclosure, causing the discharge pressure of the secondary vacuum pump P1 to increase and the speed to decrease of rotation (curve V on the figure 2 ).
- the discharge module of the pipe 10 opens, thereby limiting the increase in the discharge pressure of the pump to secondary vacuum P1.
- the gas flow is absorbed by the first two pumping stages T1, T2 of the primary vacuum pump 2, then is evacuated at the outlet of the second pumping stage T2, towards the discharge 5 of the primary vacuum pump 2 by the module load shedding.
- the processing unit 9 can start a pressure down cycle.
- the processing unit 9 controls the speed of rotation of the secondary vacuum pump 3 (curve V on the figure 2 ) as a function of an operating parameter of the secondary vacuum pump 3, such as the power consumed by the motor 7, (curve P on the figures 2 and 3 ), to increase the flow generated by the secondary vacuum pump SoR so that the flow generated by the secondary vacuum pump SoR remains greater than 1.3 times the flow generated by the primary vacuum pump Sol and less than 4.5 times the flow generated by the Sol primary vacuum pump in the example shown in the figure 3 (curve R).
- the processing unit 9 controls the increase in the speed of rotation (curve V on the figure 2 between tl and t2), causing the increase in the ratio of the flow rates generated from 1, 3 to 4, 5.
- the power consumed then stabilizes around 17kW ( figure 3 ). This power consumed is due to the maintenance of effective compression at the discharge of the secondary vacuum pump 3 and, mechanically and thermally acceptable, for the primary vacuum pump 2 and the secondary vacuum pump 3.
- a safety limit can be provided for the power consumed by the secondary vacuum pump 3. If the value of the motor parameter 7 of the secondary vacuum pump 3 is greater than a predefined safety threshold beyond a second predetermined duration, the reduction in the rotation speed of the secondary vacuum pump 3 is forced. This precaution applies more particularly in the case of airlocks of large volumes, for example greater than 100 m 3 , for which the pumping groups have been designed for small volumes of the order of 2m 3 to 20m 3 . This protects against thermal overheating of the secondary vacuum pump 3.
- the ratio of the flow generated by the secondary vacuum pump SoR to the flow generated by the primary vacuum pump Sol remains between 1, 3 and 4, 5.
- Maintaining the ratio of the generated flows lower than 4.5 allows the flow generated by the secondary vacuum pump SoR to be admissible by the primary vacuum pump 2. This limits overconsumption and the secondary vacuum pump 3 still ensures compression.
- the pressure difference between the suction and the discharge of the secondary vacuum pump 3 then remains less than a value between 150 and 350 mbar.
- the secondary vacuum pump 3 is no longer "short-circuited", as it was in a device of the prior art.
- the secondary vacuum pump 3 of the pumping group 1 according to the invention is on the contrary, used as if it were the real first pumping stage of the primary vacuum pump 2 thanks to the adapted ratio of the flow rates generated SoR and Sol.
- the secondary vacuum pump 3 is therefore effective almost from atmospheric pressure (curve A on the figure 4 from tl).
- the efficiency of the secondary vacuum pump of the device of the prior art catches up with that of the secondary vacuum pump 3 of the pumping unit 1 that around 5 mbar (tb).
- the discharge module being only little used, the discharge module wears less quickly and is less noisy. Likewise, little gas circulates in the recirculation line 10, which prevents overheating of the secondary vacuum pump 3 by these previously compressed hot gases.
- the setpoint for the rotation speed of the secondary vacuum pump 3 is fixed at its maximum value 70 Hz.
- the discharge pressure of the secondary vacuum pump P1 decreases, reducing the power consumed by the secondary vacuum pump (curve P of figures 2 and 3 ).
- the power consumed is of the order of 2 kW.
- pumping by the primary and secondary vacuum pumps 2, 3 can be carried out conventionally without adapting the speed of rotation of the secondary vacuum pump 3 because the pumping flows and the power consumed are weak.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Applications Or Details Of Rotary Compressors (AREA)
- Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
Description
La présente invention concerne un procédé de descente en pression dans un sas de chargement et de déchargement (ou « load-lock » en anglais) d'un substrat, tel qu'un écran plat d'affichage (« ou flat panel display » en anglais) ou un substrat photovoltaïque, depuis une pression atmosphérique vers une basse pression pour le chargement et le déchargement du substrat dans une chambre de traitement maintenue à basse pression. La présente invention concerne également un groupe de pompage associé pour la mise en œuvre dudit procédé de descente en pression.The present invention relates to a method of lowering pressure in a lock loading and unloading (or "load-lock" in English) of a substrate, such as a flat screen display ("or flat panel display" in English) or a photovoltaic substrate, from atmospheric pressure to low pressure for loading and unloading the substrate in a treatment chamber maintained at low pressure. The present invention also relates to an associated pumping group for the implementation of said pressure lowering method.
Un procédé de descente en pression et un groupe de pompage de ce type sont divulgués dans le document
Dans certains procédés de fabrication, une étape importante consiste à traiter un substrat sous atmosphère contrôlée à très basse pression dans une chambre de procédés. Pour maintenir une cadence acceptable et pour éviter la présence de toute impureté et de toute pollution, l'atmosphère environnant le substrat est d'abord descendu à basse pression par un sas de chargement et de déchargement communiquant avec la chambre de procédés.In certain manufacturing processes, an important step consists in treating a substrate under a controlled atmosphere at very low pressure in a process chamber. To maintain an acceptable rate and to avoid the presence of any impurity and any pollution, the atmosphere surrounding the substrate is first lowered at low pressure by a loading and unloading lock communicating with the process chamber.
Pour cela, le sas comporte une enceinte étanche dont une première porte met en communication l'intérieur de l'enceinte avec une zone sous pression atmosphérique, telle qu'une salle blanche, pour le chargement d'au moins un substrat. L'enceinte du sas est raccordée à un groupe de pompage permettant de descendre la pression dans l'enceinte jusqu'à atteindre une basse pression appropriée similaire à celle régnant dans la chambre de procédés de manière à pouvoir transférer le substrat vers la chambre de procédés. Le sas comporte en outre une deuxième porte pour le déchargement du substrat dans la chambre de procédés après avoir été mis sous vide. Ce même sas est généralement également utilisé pour la remontée en pression du substrat à l'issue de son traitement, et son déchargement à pression atmosphérique.For this, the airlock includes a sealed enclosure, a first door of which communicates the interior of the enclosure with an area under atmospheric pressure, such as a clean room, for loading at least one substrate. The airlock enclosure is connected to a pumping unit allowing the pressure in the enclosure to be lowered until an appropriate low pressure similar to that prevailing in the process chamber is reached so as to be able to transfer the substrate to the process chamber . The airlock also has a second door for discharging the substrate into the process chamber after being placed under vacuum. This same airlock is generally also used for the pressure rise of the substrate after its treatment, and its unloading at atmospheric pressure.
On comprend cependant que chaque chargement ou déchargement de substrats nécessite de descendre puis de remonter alternativement la pression dans l'enceinte du sas, ce qui implique l'intervention fréquente du groupe de pompage. On comprend également que l'établissement du vide dans l'enceinte du sas n'est pas instantané et que cela constitue une limite à la vitesse globale du processus de fabrication. Cette limite est d'autant plus sensible lorsque les substrats sont de grande dimension. Tel est le cas notamment, pour la fabrication des écrans plats d'affichage ou de substrats photovoltaïques, l'enceinte du sas ayant nécessairement le volume approprié pour contenir un ou plusieurs écrans plats. Par exemple, actuellement, les enceintes des sas utilisées pour la fabrication des écrans plats ont des gros volumes, généralement de l'ordre de 500 à 1000 litres, et dépassant parfois 5000 litres, qu'il faut donc pomper le plus rapidement possible.It is understood, however, that each loading or unloading of substrates requires lowering and then alternately raising the pressure in the airlock enclosure, which implies the frequent intervention of the pumping group. It is also understood that the establishment of the vacuum in the airlock enclosure is not instantaneous and that this constitutes a limit to the overall speed of the manufacturing process. This limit is all the more sensitive when the substrates are large. This is particularly the case, for the manufacture of flat display screens or photovoltaic substrates, the enclosure of the airlock necessarily having the appropriate volume to contain one or more flat screens. For example, currently, the chambers of airlocks used for the manufacture of flat screens have large volumes, generally of the order of 500 to 1000 liters, and sometimes exceeding 5000 liters, which must therefore be pumped as quickly as possible.
On utilise pour cela des groupes de pompage particulièrement puissants, notamment pour assurer le pompage à l'ouverture du sas, lorsque la pression dans l'enceinte est à pression atmosphérique.Particularly powerful pumping groups are used for this, in particular for ensuring pumping at the opening of the airlock, when the pressure in the enclosure is at atmospheric pressure.
Généralement, le groupe de pompage comporte une ou plusieurs pompes à vide primaires et une pompe à vide secondaire, telle qu'une pompe à vide monoétagée de type Roots. La pompe à vide secondaire est agencée en amont de la pompe primaire dans le sens d'écoulement des gaz à pomper. Elle a pour principal but de « booster » la vitesse de pompage globale du groupe de pompage à basse pression.Generally, the pumping unit comprises one or more primary vacuum pumps and a secondary vacuum pump, such as a single-stage vacuum pump of the Roots type. The secondary vacuum pump is arranged upstream of the primary pump in the direction of flow of the gases to be pumped. Its main purpose is to “boost” the overall pumping speed of the low pressure pumping group.
Le débit engendré par la pompe à vide secondaire peut être de l'ordre de cinq fois le débit engendré par la pompe primaire. Du fait du fort flux gazeux à l'ouverture du sas, une importante pression est générée au refoulement de la pompe à vide secondaire, pouvant atteindre jusqu'à 4 bar (ou 3 bar relatifs). Cette forte surpression provoque une consommation très importante de la pompe à vide secondaire et un engorgement à l'aspiration de la pompe à vide primaire, constituant un risque de dysfonctionnement à la fois pour la pompe à vide primaire et pour la pompe à vide secondaire.The flow generated by the secondary vacuum pump can be of the order of five times the flow generated by the primary pump. Due to the strong gas flow at the opening of the airlock, a significant pressure is generated at the discharge of the secondary vacuum pump, which can reach up to 4 bar (or 3 bar relative). This high overpressure causes a very high consumption of the secondary vacuum pump and a congestion at the suction of the primary vacuum pump, constituting a risk of malfunction for both the primary vacuum pump and for the secondary vacuum pump.
Pour éviter cela, une solution connue consiste à agencer une canalisation raccordant l'entrée de la pompe à vide primaire à l'entrée de la pompe à vide secondaire. La canalisation est équipée d'un clapet de recirculation (ou « bypass » en anglais), taré pour s'ouvrir lorsque la différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire devient trop importante, généralement taré pour s'ouvrir pour une différence de pression maximale comprise entre 50 et 80 mbar. Ainsi, le clapet de recirculation s'ouvre au début de la descente en pression, pour faire circuler le surplus du flux gazeux du refoulement vers l'aspiration de la pompe à vide secondaire. Puis, pour une différence de pression amont/aval de la pompe à vide secondaire inférieure à 50 ou 80 mbar, le clapet de recirculation se ferme. A haute pression, la descente en pression est donc uniquement assurée par la pompe à vide primaire, le rôle de la pompe à vide secondaire n'est alors plus que de participer à la « recirculation » du flux gazeux.To avoid this, a known solution consists in arranging a pipe connecting the inlet of the primary vacuum pump to the inlet of the secondary vacuum pump. The pipeline is fitted with a recirculation valve (or “bypass” in English), calibrated to open when the pressure difference between the suction and the discharge of the secondary vacuum pump becomes too large, generally tared for s '' open for a maximum pressure difference between 50 and 80 mbar. Thus, the recirculation valve opens at the start of the pressure drop, to circulate the excess gas flow from the discharge to the suction of the secondary vacuum pump. Then, for an upstream / downstream pressure difference of the secondary vacuum pump less than 50 or 80 mbar, the recirculation valve closes. At high pressure, the pressure drop is therefore only ensured by the primary vacuum pump, the role of the secondary vacuum pump is then only to participate in the "recirculation" of the gas flow.
Le clapet de recirculation permet ainsi de protéger la pompe à vide primaire en dérivant le surplus de flux gazeux. Cette recirculation permet également de protéger thermiquement la pompe à vide secondaire en évitant que sa pression de refoulement ne devienne trop importante.The recirculation valve thus protects the primary vacuum pump by diverting the excess gas flow. This recirculation also thermally protects the secondary vacuum pump by preventing its discharge pressure from becoming too high.
La baisse de la pression dans le sas engendre ensuite la réduction de pression au refoulement de la pompe à vide secondaire et la fermeture du clapet de recirculation, permettant ainsi à la pompe à vide secondaire de commencer à comprimer les gaz à pomper à partir d'une pression dans le sas généralement de l'ordre de 200 mbar.The drop in pressure in the airlock then generates the pressure reduction on the discharge of the secondary vacuum pump and the closing of the recirculation valve, thus allowing the secondary vacuum pump to start compressing the gases to be pumped from a pressure in the airlock generally of the order of 200 mbar.
Ce dispositif de l'état de la technique peut cependant présenter certains inconvénients.This prior art device can however have certain drawbacks.
Au démarrage de la descente en pression, la vitesse de pompage globale initiale du groupe de pompage est faible car le pompage est uniquement assuré par la pompe à vide primaire.At the start of the pressure drop, the initial overall pumping speed of the pumping unit is low because pumping is only ensured by the primary vacuum pump.
En outre, jusqu'à ce que la pression dans le sas atteigne quelques mbar, la puissance consommée par la pompe à vide secondaire est importante et perdue du fait de la recirculation du flux gazeux.In addition, until the pressure in the airlock reaches a few mbar, the power consumed by the secondary vacuum pump is high and lost due to the recirculation of the gas flow.
Un autre problème réside dans le fait que le clapet de recirculation fonctionne de manière pulsatoire, s'ouvrant et se refermant cycliquement très rapidement notamment du fait du principe de pompage cyclique de la pompe à vide secondaire volumétrique. De cela peuvent résulter des risques d'usure mécanique prématurée du clapet de recirculation et donc des risques de fuites. Egalement, le fonctionnement pulsatoire du clapet de recirculation peut être à l'origine de bruits parasites.Another problem lies in the fact that the recirculation valve operates in a pulsating manner, opening and closing cyclically very quickly, in particular due to the principle of cyclic pumping of the volumetric secondary vacuum pump. This may result in the risks of premature mechanical wear of the recirculation valve and therefore the risk of leaks. Also, the pulsating operation of the recirculation valve can be the source of noise.
Par ailleurs, les gaz qui circulent dans la canalisation du clapet de recirculation sont chauds, du fait de la compression de la pompe à vide secondaire. Ces gaz chauds recyclés peuvent également contribuer au réchauffement de la pompe à vide secondaire.Furthermore, the gases which circulate in the pipe of the recirculation valve are hot, due to the compression of the secondary vacuum pump. These recycled hot gases can also contribute to the heating of the secondary vacuum pump.
Un des buts de la présente invention est donc de proposer un procédé de descente en pression dans un sas de chargement et de déchargement et un groupe de pompage associé qui résolvent au moins en partie les problèmes de l'état de la technique, en permettant notamment d'augmenter la vitesse de pompage au démarrage de la descente en pression tout en réduisant la puissance consommée par la pompe à vide secondaire.One of the aims of the present invention is therefore to propose a process for lowering pressure in a loading and unloading airlock and an associated pumping unit which at least partially solve the problems of the state of the art, by allowing in particular increase the pumping speed at the start of the pressure drop while reducing the power consumed by the secondary vacuum pump.
Un autre but de la présente invention est de protéger la pompe à vide primaire et la pompe à vide secondaire des risques d'endommagement liés au surplus de flux gazeux à l'ouverture du sas à pression atmosphérique.Another object of the present invention is to protect the primary vacuum pump and the secondary vacuum pump from the risks of damage linked to the excess gas flow when the airlock is opened at atmospheric pressure.
Un autre but de la présente invention est de limiter les risques d'usure du clapet de recirculation et le réchauffement de la pompe à vide secondaire par les gaz chauds « recyclés ».Another object of the present invention is to limit the risks of wear of the recirculation valve and the heating of the secondary vacuum pump by the “recycled” hot gases.
A cet effet, l'invention a pour objet un procédé de descente en pression dans un sas de chargement et de déchargement d'un substrat à pression atmosphérique par un groupe de pompage comportant une pompe à vide primaire et une pompe à vide secondaire agencée en amont de ladite pompe à vide primaire dans le sens d'écoulement des gaz à pomper, caractérisé en ce qu'au cours de la descente en pression et jusqu'à ce que la pression dans le sas de chargement et de déchargement atteigne un seuil de basse pression prédéfini, on contrôle la vitesse de rotation de la pompe à vide secondaire en fonction d'un paramètre de fonctionnement de la pompe à vide secondaire pour augmenter le débit engendré par la pompe à vide secondaire de sorte que le débit engendré par la pompe à vide secondaire soit compris dans une plage dont la valeur haute correspond à six fois le débit engendré par la pompe à vide primaire et la valeur basse à 1, 3 fois le débit engendré par la pompe à vide primaire.To this end, the subject of the invention is a process for lowering pressure in an airlock for loading and unloading a substrate at atmospheric pressure by a pumping group comprising a primary vacuum pump and a secondary vacuum pump arranged in upstream of said primary vacuum pump in the direction of flow of the gases to be pumped, characterized in that during the pressure drop and until the pressure in the loading and unloading lock reaches a threshold of predefined low pressure, the rotation speed of the secondary vacuum pump is controlled according to an operating parameter of the secondary vacuum pump to increase the flow generated by the secondary vacuum pump so that the flow generated by the pump with no-load secondary is included in a range whose high value corresponds to six times the flow generated by the primary vacuum pump and the low value at 1.3 times the flow generated by the primary vacuum pump.
Selon une ou plusieurs caractéristiques du procédé de descente en pression, prise seule ou en combinaison,
- le paramètre de fonctionnement de la pompe à vide secondaire est un paramètre du moteur de la pompe à vide secondaire,
- on commence à contrôler la vitesse de rotation de la pompe à vide secondaire en fonction d'un paramètre de fonctionnement de la pompe à vide secondaire lorsque l'on détecte que la valeur d'un paramètre de fonctionnement de la pompe à vide secondaire dépasse un seuil de lancement prédéfini pendant une première durée prédéfinie,
- si la valeur d'un paramètre de fonctionnement de la pompe à vide secondaire est supérieure à un seuil de sécurité prédéfini au-delà d'une deuxième durée prédéterminée, on force la diminution de la vitesse de rotation de la pompe à vide secondaire,
- si la valeur d'un paramètre de fonctionnement de la pompe à vide secondaire est inférieure à un seuil d'attente prédéfini au-delà d'une troisième durée prédéterminée, on contrôle la vitesse de rotation de la pompe à vide secondaire à une vitesse de rotation fixe réduite.
- the operating parameter of the secondary vacuum pump is a parameter of the motor of the secondary vacuum pump,
- we start to control the rotation speed of the secondary vacuum pump as a function of an operating parameter of the secondary vacuum pump when it is detected that the value of an operating parameter of the secondary vacuum pump exceeds a predefined launch threshold for a first predefined duration,
- if the value of an operating parameter of the secondary vacuum pump is greater than a predefined safety threshold beyond a second predetermined duration, the speed of rotation of the secondary vacuum pump is reduced,
- if the value of an operating parameter of the secondary vacuum pump is less than a predefined waiting threshold beyond a third predetermined duration, the speed of rotation of the secondary vacuum pump is controlled at a speed of reduced fixed rotation.
L'invention a aussi pour objet un groupe de pompage comportant une pompe à vide primaire et une pompe à vide secondaire, ladite pompe à vide secondaire étant agencée en amont de ladite pompe à vide primaire dans le sens d'écoulement des gaz à pomper et comportant un variateur de fréquence, caractérisé en ce que la pompe à vide secondaire comporte une unité de contrôle reliée au variateur de fréquence, configuré pour contrôler la vitesse de rotation de la pompe à vide secondaire en fonction d'un signal représentatif d'un paramètre de fonctionnement de la pompe à vide secondaire, de sorte qu'au cours de la descente en pression et jusqu'à ce que la pression dans le sas de chargement et de déchargement atteigne un seuil de basse pression prédéfini, le débit engendré par la pompe à vide secondaire soit augmenté et compris dans une plage dont la valeur haute correspond à six fois le débit engendré par la pompe à vide primaire et la valeur basse, à 1,3 fois le débit engendré par la pompe à vide primaire.The invention also relates to a pumping unit comprising a primary vacuum pump and a secondary vacuum pump, said secondary vacuum pump being arranged upstream of said primary vacuum pump in the direction of flow of the gases to be pumped and comprising a frequency converter, characterized in that the secondary vacuum pump comprises a control unit connected to the frequency converter, configured to control the speed of rotation of the secondary vacuum pump as a function of a signal representative of a parameter of the secondary vacuum pump, so that during the pressure drop and until the pressure in the loading and unloading airlock reaches a predefined low pressure threshold, the flow generated by the pump secondary vacuum is increased and included in a range whose high value corresponds to six times the flow generated by the primary vacuum pump and the low value, to 1.3 times the flow generated by the primary vacuum pump.
Selon un exemple de réalisation particulier, la pompe à vide primaire comporte un module de délestage d'un étage de pompage.According to a particular embodiment, the primary vacuum pump comprises a load shedding module of a pumping stage.
Le signal représentatif d'un paramètre de fonctionnement de la pompe à vide secondaire est par exemple un paramètre du moteur de la pompe à vide secondaire, tel que le courant ou la puissance.The signal representative of an operating parameter of the secondary vacuum pump is for example a parameter of the motor of the secondary vacuum pump, such as the current or the power.
Selon un exemple de réalisation, le groupe de pompage comporte une canalisation de recirculation raccordant l'entrée de la pompe à vide primaire à l'entrée de la pompe à vide secondaire, la canalisation de recirculation comportant un module de décharge configuré pour s'ouvrir dès que la pression d'aspiration de la pompe à vide primaire dépasse la pression d'aspiration de la pompe à vide secondaire d'une valeur de dépassement prédéfinie comprise entre 100 et 400 mbar.According to an exemplary embodiment, the pumping unit comprises a recirculation line connecting the inlet of the primary vacuum pump to the inlet of the secondary vacuum pump, the recirculation line comprising a discharge module configured to open as soon as the suction pressure of the primary vacuum pump exceeds the suction pressure of the secondary vacuum pump by a predefined overshoot value between 100 and 400 mbar.
La pompe à vide secondaire est par exemple une pompe à vide de type ROOTS.The secondary vacuum pump is for example a ROOTS type vacuum pump.
En maintenant le débit engendré par la pompe à vide secondaire supérieur à 1, 3 fois le débit engendré par la pompe à vide primaire et inférieur à six fois le débit engendré par la pompe à vide primaire au cours de la descente en pression et jusqu'à ce que la pression dans le sas de chargement et de déchargement atteigne un seuil de basse pression prédéfini, on adapte le rapport des débits engendrés entre la pompe à vide primaire et la pompe à vide secondaire pour qu'il soit optimal. Plus précisément, on maintient un débit engendré par la pompe à vide secondaire admissible pour le fort flux gazeux initial, c'est-à-dire inférieur à six fois le débit engendré par la pompe à vide primaire. Simultanément, on maintient un débit engendré optimisé pour la pompe à vide primaire, c'est-à-dire supérieur à 1, 3 fois le débit engendré par la pompe à vide primaire pour assurer au plus tôt, une compression des gaz.Maintaining the flow generated by the secondary vacuum pump greater than 1.3 times the flow generated by the primary vacuum pump and less than six times the flow generated by the primary vacuum pump during the pressure drop and up to as the pressure in the loading and unloading airlock reaches a predefined low pressure threshold, the ratio of the flow rates generated between the primary vacuum pump and the secondary vacuum pump is adapted so that it is optimal. More precisely, a flow generated by the secondary vacuum pump admissible for the high initial gas flow is maintained, that is to say less than six times the flow generated by the primary vacuum pump. Simultaneously, an optimized generated flow is maintained for the primary vacuum pump, that is to say greater than 1.3 times the flow generated by the primary vacuum pump to ensure gas compression as soon as possible.
La différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire reste alors inférieure à une valeur comprise entre 150 et 300 mbar. La canalisation et le clapet de recirculation du dispositif de l'art antérieur, taré pour s'ouvrir pour un différentiel de pression de la pompe à vide secondaire compris entre 50 et 80 mbar, peuvent alors être supprimés. Par sécurité, le groupe de pompage peut toutefois comporter un module de décharge configuré pour s'ouvrir dès que la différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire dépasse une valeur plus élevée, comprise entre 100 et 400 mbar, selon la valeur du rapport des débits qui est retenue et selon les réglages de sécurité mécanique, permettant de protéger les pompes à vide notamment le temps que le contrôle de vitesse soit effectif.The pressure difference between the suction and the discharge of the secondary vacuum pump then remains less than a value between 150 and 300 mbar. The pipe and the recirculation valve of the device of the prior art, calibrated to open for a pressure differential of the secondary vacuum pump of between 50 and 80 mbar, can then be eliminated. For safety, the pumping unit can however include a discharge module configured to open as soon as the pressure difference between the suction and the discharge of the secondary vacuum pump exceeds a higher value, between 100 and 400 mbar , according to the value of the flow rate ratio which is selected and according to the mechanical safety settings, making it possible to protect the vacuum pumps in particular while the speed control is effective.
Dès que la vitesse de rotation de la pompe à vide secondaire est contrôlée, la pompe à vide secondaire n'est plus « court-circuitée », comme elle l'était au-dessus d'une pression de 200mbar dans le sas de l'état de la technique, mais elle est utilisée comme si elle était le véritable premier étage de pompage de la pompe à vide primaire. Les caractéristiques de fonctionnement de la pompe à vide secondaire sont ainsi adaptées aux capacités de la pompe à vide primaire de sorte que la pompe à vide secondaire peut être efficace quasiment dès la pression atmosphérique. De cela résulte une baisse importante de la puissance consommée ainsi qu'une augmentation de la vitesse de pompage globale du groupe de pompage au début de la descente en pression, et donc, une réduction du temps de descente en pression dans le sas. Par exemple, dans la gamme de pression allant de 1000 mbar à 20mbar, la vitesse de pompage augmente de 20 à 50%, comparée à la vitesse de pompage des dispositifs de l'art antérieur. De même, le temps global de descente en pression dans l'enceinte d'un sas de 500 litres entre une pression voisine de 1000 mbar à une pression de transfert de l'ordre de 0,1 mbar passe de 25 à 20 secondes, soit une réduction de l'ordre de 20%.As soon as the rotation speed of the secondary vacuum pump is controlled, the secondary vacuum pump is no longer "short-circuited", as it was above a pressure of 200mbar in the airlock of the state of the art, but it is used as if it were the real first pumping stage of the primary vacuum pump. The operating characteristics of the secondary vacuum pump are thus adapted to the capacities of the primary vacuum pump so that the secondary vacuum pump can be effective almost from atmospheric pressure. This results in a significant drop in the power consumed as well as an increase in the overall pumping speed of the pumping unit at the start of the pressure drop, and therefore, a reduction in the pressure drop time in the airlock. For example, in the pressure range from 1000 mbar to 20 mbar, the pumping speed increases from 20 to 50%, compared to the pumping speed of the devices of the prior art. Similarly, the overall time of pressure drop in the enclosure of a 500-liter airlock between a pressure close to 1000 mbar at a transfer pressure of the order of 0.1 mbar goes from 25 to 20 seconds, i.e. a reduction of around 20%.
En outre, étant donné que le module de décharge s'ouvre à une pression plus haute que le clapet de recirculation de l'état de la technique et qu'ensuite le rapport des débits entre les pompes à vide primaire et secondaire est optimisé, la pression de refoulement de la pompe à vide secondaire diminue rapidement de sorte que le module de décharge n'est que très peu de temps ouvert. Etant peu sollicité, le module de décharge s'use moins vite et est moins bruyant. En outre, peu de gaz circule dans la canalisation de recirculation, ce qui évite la surchauffe de la pompe à vide secondaire par les gaz comprimés chauds.In addition, since the discharge module opens at a higher pressure than the prior art recirculation valve and, subsequently, the flow ratio between the primary and secondary vacuum pumps is optimized, the discharge pressure of the secondary vacuum pump decreases rapidly so that the discharge module is only open for a very short time. Being little used, the discharge module wears less quickly and is less noisy. In addition, little gas circulates in the recirculation line, which prevents overheating of the secondary vacuum pump by hot compressed gases.
D'autres caractéristiques et avantages de l'invention ressortiront de la description suivante, donnée à titre d'exemple, sans caractère limitatif, en regard des dessins annexés sur lesquels:
- la
figure 1 représente une vue schématique d'un groupe de pompage selon l'invention, - la
figure 2 est un graphique illustrant une descente en pression dans un sas de chargement et de déchargement raccordé au groupe de pompage de lafigure 1 , avec en abscisse : la pression dans l'enceinte du sas (en mbar), sur l'ordonnée de droite : la fréquence de rotation de la pompe à vide secondaire (en Hz) et sur l'ordonnée de gauche : la puissance consommée par la pompe à vide secondaire (en kW), - la
figure 3 est un graphique analogue à lafigure 2 avec sur l'ordonnée de droite : le rapport du débit engendré de la pompe à vide secondaire sur le débit engendré de la pompe à vide primaire, et - la
figure 4 est un graphique illustrant les vitesses de pompage (en m3/h) d'une pompe à vide primaire seule, du groupe de pompage selon l'invention et d'un dispositif de pompage de l'état de la technique, au cours d'une descente en pression en fonction de la pression dans l'enceinte du sas de chargement et de déchargement (en mbar).
- the
figure 1 represents a schematic view of a pumping unit according to the invention, - the
figure 2 is a graph illustrating a pressure drop in a loading and unloading airlock connected to the pumping unit of thefigure 1 , with the abscissa: the pressure in the airlock enclosure (in mbar), on the ordinate on the right: the rotation frequency of the secondary vacuum pump (in Hz) and on the ordinate on the left: the power consumed by the secondary vacuum pump (in kW), - the
figure 3 is a graph similar to thefigure 2 with on the right ordinate: the ratio of the flow generated from the secondary vacuum pump to the flow generated from the primary vacuum pump, and - the
figure 4 is a graph illustrating the pumping speeds (in m 3 / h) of a primary vacuum pump alone, of the pumping group according to the invention and of a pumping device of the state of the art, during d '' a pressure drop as a function of the pressure in the enclosure of the loading and unloading airlock (in mbar).
Sur ces figures, les éléments identiques portent les mêmes numéros de référence.In these figures, identical elements have the same reference numbers.
On définit par « pression atmosphérique », la pression environnante à l'extérieur du sas de chargement et de déchargement du substrat, telle que la pression régnant dans une salle dans laquelle évoluent les opérateurs de salle blanche, c'est-à-dire une pression de l'ordre de 105 Pascal (1000 mbar) ou légèrement supérieure pour privilégier le sens du flux vers l'extérieur de l'enceinte.We define by "atmospheric pressure", the surrounding pressure outside the airlock for loading and unloading of the substrate, such as the pressure prevailing in a room in which clean room operators work, that is to say a pressure of the order of 10 5 Pascal (1000 mbar) or slightly higher to favor the direction of flow towards the outside of the enclosure.
On définit par « débit engendré » (ou volume engendré), la cylindrée correspondante au volume entraîné par les rotors de la pompe à vide multipliée par le nombre de tours minute.We define by "generated flow" (or generated volume), the displacement corresponding to the volume driven by the rotors of the vacuum pump multiplied by the number of revolutions per minute.
La
De façon connue en soi, le sas de chargement et de déchargement comporte une enceinte étanche dont une première porte met en communication l'intérieur de l'enceinte avec une zone sous pression atmosphérique, telle qu'une salle blanche, pour le chargement d'au moins un substrat de grand volume, tel qu'un écran plat d'affichage (« flat panel display » en anglais) ou un substrat photovoltaïque. De tels sas présentent un volume généralement compris entre 500 et 5000 litres.In a manner known per se, the loading and unloading airlock comprises a sealed enclosure, a first door of which communicates the interior of the enclosure with an area under atmospheric pressure, such as a clean room, for loading at least one large-volume substrate, such as a flat panel display or a photovoltaic substrate. Such airlocks have a volume generally between 500 and 5000 liters.
Le sas comporte en outre une deuxième porte pour le déchargement du substrat dans la chambre de procédés après mise sous vide, ainsi qu'un dispositif d'introduction d'un gaz neutre, notamment pour le retour à la pression atmosphérique après traitement du substrat.The airlock also includes a second door for discharging the substrate into the process chamber after vacuum, as well as a device for introducing a neutral gas, in particular for returning to atmospheric pressure after treatment of the substrate.
Le groupe de pompage 1 comporte une pompe à vide primaire 2 et une pompe à vide secondaire 3 agencée en amont de la pompe à vide primaire 2 dans le sens d'écoulement des gaz à pomper.The
La pompe à vide primaire 2 comporte par exemple une pompe à vide sèche multiétagée, à lobes rotatifs tels que de type Roots avec deux ou trois lobes (bi-lobes, tri-lobes). Selon d'autres modes de réalisation non décrits, la pompe à vide primaire comporte plusieurs pompes en série ou en parallèle. Par ailleurs, d'autres principes de pompage classiques peuvent être utilisés pour la pompe à vide primaire.The
La pompe à vide primaire 2 schématisée sur la
De façon générale, une pompe à vide à lobes rotatifs " Roots " comprend deux rotors de profils identiques, portés par deux arbres s'étendant dans les étages de pompage T1, T2, T3, T4, T5 et entraînés par un moteur de la pompe à vide primaire 2 (non représenté) pour tourner à l'intérieur d'un stator en sens opposé. Lors de la rotation, le gaz aspiré est emprisonné dans l'espace libre compris entre les rotors et le stator, puis il est refoulé. Le fonctionnement s'effectue sans aucun contact mécanique entre les rotors et le stator de la pompe à vide primaire 2, ce qui permet l'absence totale d'huile dans les étages de pompage T1, T2, T3, T4, T5.In general, a "Roots" rotary lobe vacuum pump comprises two rotors of identical profiles, carried by two shafts extending in the pumping stages T1, T2, T3, T4, T5 and driven by a pump motor. primary vacuum 2 (not shown) to rotate inside a stator in the opposite direction. During rotation, the sucked gas is trapped in the free space between the rotors and the stator, then it is pushed back. The operation is carried out without any mechanical contact between the rotors and the stator of the
Dans l'exemple illustré, le premier étage de pompage T1 de la pompe à vide primaire 2 présente un débit engendré So1 de l'ordre de 600m3/h, le deuxième étage de pompage T2 présente un débit engendré So2 de l'ordre de 400m3/h, le troisième étage de pompage T3 présente un débit engendré So3 de l'ordre de 200m3/h et les deux derniers étage de pompage T4 et T5 présentent un débit engendré So4, So5 de l'ordre de 100m3/h. Les débits engendrés variant en fonction de la gamme de pression, ces valeurs correspondent aux valeurs maximales, à flux de pompage constant, avec une vitesse de rotation de la pompe à vide primaire 2 en fonctionnement fixe et de l'ordre de 65Hz.In the example illustrated, the first pumping stage T1 of the
La pompe à vide primaire 2 comporte en outre un clapet anti-retour 6 en sortie du dernier étage de pompage T5, au niveau du refoulement 5, pour éviter le retour des gaz pompés dans la pompe à vide primaire 2.The
La pompe à vide secondaire 3 est, comme la pompe à vide primaire 2, une pompe à vide volumétrique, c'est-à-dire une pompe à vide qui, à l'aide de pistons, rotors, palettes, soupapes, aspire, transfère puis refoule le gaz à pomper.The
La pompe à vide secondaire 3 est par exemple une pompe à vide monoétagée (ne présentant qu'un unique étage de pompage), à rotors tel que de type Roots ou d'un principe similaire, tel que de type Claw.The
En fonctionnement, le débit engendré SoR maximal de la pompe à vide secondaire 3 est par exemple de l'ordre de 3000m3/h à vitesse de rotation maximale (soit à environ 70Hz), dans la gamme de pression optimale.In operation, the maximum flow generated SoR of the
La pompe à vide secondaire 3 comporte un moteur 7, tel qu'un moteur asynchrone, un variateur de fréquence 8 pour piloter le moteur 7 entraînant les rotors et une unité de contrôle 9 reliée au variateur de fréquence 8.The
Au cours de la descente en pression dans le sas de chargement et de déchargement à pression atmosphérique et jusqu'à ce que la pression dans le sas atteigne un seuil de basse pression prédéfini, l'unité de contrôle 9 est configurée pour contrôler la vitesse de rotation des rotors de la pompe à vide secondaire 3 en fonction d'un signal représentatif d'un paramètre de fonctionnement de la pompe à vide secondaire 3 pour augmenter le débit engendré de sorte que le débit engendré par la pompe à vide secondaire SoR soit compris dans une plage dont la valeur haute correspond à six fois le débit engendré par la pompe à vide primaire Sol et la valeur basse à 1, 3 fois le débit engendré par la pompe à vide primaire Sol.During the pressure drop in the airlock for loading and unloading at atmospheric pressure and until the pressure in the airlock reaches a predefined low pressure threshold, the
Le seuil de basse pression prédéfini est par exemple 20 mbar. En deçà, la vitesse de rotation de la pompe à vide secondaire 3 est commandée à sa valeur maximale, c'est-à-dire 70Hz dans le présent exemple.The predefined low pressure threshold is for example 20 mbar. Below this, the speed of rotation of the
La différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire reste alors inférieure à une valeur comprise entre 150 et 300 mbar.The pressure difference between the suction and the discharge of the secondary vacuum pump then remains less than a value between 150 and 300 mbar.
Le signal représentatif d'un paramètre de fonctionnement est par exemple la pression de refoulement de la pompe à vide secondaire P1 ou un paramètre du moteur 7 de la pompe à vide secondaire 3.The signal representative of an operating parameter is for example the discharge pressure of the secondary vacuum pump P1 or a parameter of the
Dans ce dernier cas, le paramètre du moteur 7 de la pompe à vide secondaire 3 peut être le courant, représentatif de la puissance consommée, ou directement la puissance consommée. Ces signaux peuvent être reçus du variateur de vitesse 8 raccordé au moteur 7. Ainsi, le contrôle de la pompe à vide secondaire 3 est autonome car il ne nécessite ni information provenant du sas de chargement et de déchargement, ni ajout de capteur de pression à l'entrée d'admission 4 de la pompe à vide primaire 2.In the latter case, the parameter of the
Le contrôle de la vitesse de rotation des rotors de la pompe à vide secondaire 3 en fonction d'un signal représentatif d'un paramètre de fonctionnement de la pompe à vide secondaire 3 est un asservissement en boucle fermée : lorsque la pression de refoulement P1 ou le courant moteur 7 ou la puissance augmente et que le débit engendré approche ou dépasse la valeur haute de la plage autorisée, la vitesse de rotation est ralentie, voire diminuée.The control of the rotational speed of the rotors of the
Le groupe de pompage 1 comporte en outre une canalisation 10 raccordant l'entrée 4 de la pompe à vide primaire 2 à l'entrée d'admission 11 de la pompe à vide secondaire 3.The
La canalisation 10 comporte un module de décharge, tel qu'un clapet 12 ou une vanne pilotée par l'unité de traitement 9, configuré(e) pour s'ouvrir dès que la différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire 3 dépasse une valeur de dépassement ΔP prédéfinie, comprise entre 100 et 400 mbar, la valeur de dépassement ΔP étant définie selon le ratio des débits engendrés retenu et selon les réglages de sécurité mécanique.The
Par exemple, pour un rapport des débits engendrés maximum de l'ordre de 4, 5, la différence de pression de la pompe à vide secondaire 3 reste toujours inférieure à une pression de l'ordre de 250 mbar. Le module de décharge est donc configuré pour s'ouvrir dès que la pression d'aspiration de la pompe à vide primaire P1 dépasse la pression d'aspiration de la pompe à vide secondaire Pasp d'une valeur de dépassement ΔP prédéfinie par exemple à 300mbar.For example, for a ratio of maximum generated flow rates of the order of 4.5, the pressure difference of the
Par ailleurs, pour absorber le fort flux de gaz initial provenant de la mise sous vide du sas à pression atmosphérique, on prévoit que la pompe à vide primaire 2 soit conçue pour être capable d'absorber et transférer ce fort flux gazeux avec la puissance consommée la plus faible possible. Pour cela, par exemple, la pompe à vide primaire 2 comporte un module de délestage d'un étage de pompage.Furthermore, to absorb the strong initial gas flow coming from the vacuuming of the airlock at atmospheric pressure, it is provided that the
En effet, bien que le débit engendré de la pompe à vide secondaire SoR soit adapté pour correspondre au débit engendré de la pompe à vide primaire Sol, c'est-à-dire au débit engendré par le premier étage de pompage T1 de la pompe à vide primaire 2, le deuxième ou le troisième étage de pompage T2, T3 peuvent à leur tour, limiter le débit engendré global de la pompe à vide primaire 2. Ainsi, pour que la pompe à vide primaire 2 puisse absorber ponctuellement des flux de pompage importants correspondant dans cet exemple à une pression d'aspiration P1 limitée à la pression d'ouverture du module de décharge, c'est-à-dire 300 mbar, le module de délestage est raccordé à la sortie d'un étage de pompage basse pression, tel que le deuxième étage de pompage T2.Indeed, although the flow generated from the secondary vacuum pump SoR is adapted to correspond to the flow generated from the primary vacuum pump Sol, that is to say the flow generated by the first pumping stage T1 of the pump
Le module de délestage comporte par exemple un canal 13 raccordant la sortie de l'étage basse pression (T1 ou T2) au refoulement 5 de la pompe à vide primaire 2. Le canal 13 est pourvu d'un clapet 14.The load-shedding module comprises for example a
On se réfère maintenant aux graphiques des
A l'état initial, la vitesse de rotation de la pompe à vide secondaire 3 est à une vitesse de rotation fixe réduite, par exemple de l'ordre de 30Hz afin de limiter la consommation électrique.In the initial state, the rotation speed of the
Puis, après le chargement d'un substrat à pression atmosphérique dans l'enceinte du sas de chargement et de déchargement, le sas ouvre la vanne d'isolation isolant l'enceinte à pression atmosphérique du groupe de pompage 1 (tl).Then, after the loading of a substrate at atmospheric pressure in the enclosure of the loading and unloading lock, the lock opens the isolation valve isolating the enclosure at atmospheric pressure from the pumping unit 1 (tl).
Pendant un laps de temps relativement court, de l'ordre de quelques secondes, la pompe à vide secondaire 3 comprime le surplus de gaz provenant de l'enceinte, faisant augmenter la pression de refoulement de la pompe à vide secondaire P1 et baisser la vitesse de rotation (courbe V sur la
Dès que la différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire 3 dépasse 300 mbar, le module de décharge de la canalisation 10 s'ouvre, limitant alors l'augmentation de la pression de refoulement de la pompe à vide secondaire P1. Le flux de gaz est absorbé par les deux premiers étages de pompage T1, T2 de la pompe à vide primaire 2, puis est évacué en sortie du deuxième étage de pompage T2, vers le refoulement 5 de la pompe à vide primaire 2 par le module de délestage.As soon as the pressure difference between the suction and the discharge of the
Lorsqu'un paramètre de fonctionnement de la pompe à vide secondaire 3, tel que la puissance consommée par la pompe à vide secondaire 3 (courbe P sur la
Etant donné que la puissance consommée par la pompe à vide secondaire 3 augmente, mais que le débit engendré par la pompe à vide secondaire SoR reste inférieur à 4, 5 fois le débit engendré par la pompe à vide primaire Sol, l'unité de traitement 9 commande l'augmentation de la vitesse de rotation (courbe V sur la
En outre, on peut prévoir par sécurité, un plafond pour la puissance consommée par la pompe à vide secondaire 3. Si la valeur du paramètre moteur 7 de la pompe à vide secondaire 3 est supérieure un seuil de sécurité prédéfini au-delà d'une deuxième durée prédéterminée, on force la diminution de la vitesse de rotation de la pompe à vide secondaire 3. Cette précaution s'applique plus particulièrement dans le cas de sas de gros volumes, par exemple supérieurs à 100m3, pour lesquels les groupes de pompage ont été dimensionnés pour de petits volumes de l'ordre de 2m3 à 20m3. On se prémunit ainsi d'une surchauffe thermique de la pompe à vide secondaire 3.In addition, a safety limit can be provided for the power consumed by the
On constate qu'entre la pression atmosphérique (tl) et le seuil de basse pression prédéfini, telle que 20 mbar (t2), le rapport du débit engendré par la pompe à vide secondaire SoR sur le débit engendré par la pompe à vide primaire Sol reste compris entre 1, 3 et 4, 5.It can be seen that between atmospheric pressure (tl) and the predefined low pressure threshold, such as 20 mbar (t2), the ratio of the flow generated by the secondary vacuum pump SoR to the flow generated by the primary vacuum pump Sol remains between 1, 3 and 4, 5.
Le maintien du rapport des débits engendrés inférieur à 4, 5 permet que le débit engendré par la pompe à vide secondaire SoR soit admissible par la pompe à vide primaire 2. On limite ainsi la surconsommation et la pompe à vide secondaire 3 assure tout de même une compression. La différence de pression entre l'aspiration et le refoulement de la pompe à vide secondaire 3 reste alors inférieure à une valeur comprise entre 150 et 350 mbar.Maintaining the ratio of the generated flows lower than 4.5 allows the flow generated by the secondary vacuum pump SoR to be admissible by the
La pompe à vide secondaire 3 n'est plus « court-circuitée », comme elle l'était dans un dispositif de l'état de la technique.The
A titre de comparaison, on a représenté sur la
On voit que pour le dispositif de l'état de la technique, entre 200mbar et la pression atmosphérique, la pompe à vide secondaire n'améliore pas la vitesse de pompage globale, la descente en pression étant uniquement assurée par la pompe à vide primaire. Le rôle de la pompe à vide secondaire dont la vitesse de rotation est piloté à une vitesse fixe maximale n'est alors que de participer à la recirculation du flux gazeux en surconsommant (courbes B et C entre tl et ta).It can be seen that for the device of the prior art, between 200 mbar and atmospheric pressure, the secondary vacuum pump does not improve the overall pumping speed, the pressure drop being only ensured by the primary vacuum pump. The role of the secondary vacuum pump whose speed of rotation is controlled at a maximum fixed speed is then only to participate in the recirculation of the gas flow by overconsumption (curves B and C between tl and ta).
La pompe à vide secondaire 3 du groupe de pompage 1 selon l'invention est au contraire, utilisée comme si elle était le véritable premier étage de pompage de la pompe à vide primaire 2 grâce au rapport adapté des débits engendrés SoR et Sol. La pompe à vide secondaire 3 est donc efficace quasiment dès la pression atmosphérique (courbe A sur la
De cela résulte une baisse importante de la puissance consommée par le groupe de pompage 1 ainsi qu'une augmentation de sa vitesse de pompage globale au début de la descente en pression, et donc, une réduction du temps de descente en pression dans le sas. Dans l'exemple, à 200 mbar, la vitesse de pompage globale augmente de 40% par rapport au dispositif de l'état de la technique.This results in a significant drop in the power consumed by the
En outre, le module de décharge n'étant que peu sollicité, le module de décharge s'use moins vite et est moins bruyant. De même, peu de gaz circule dans la canalisation de recirculation 10, ce qui évite la surchauffe de la pompe à vide secondaire 3 par ces gaz préalablement comprimés chauds.In addition, the discharge module being only little used, the discharge module wears less quickly and is less noisy. Likewise, little gas circulates in the
Puis, lorsque la pression dans le sas atteint le seuil de basse pression prédéfini, (t2 sur la courbe B de la
A très basse pression (au-delà de t3), par exemple dans l'attente de l'ouverture du sas vers la chambre de procédés pour le transfert du substrat, si la valeur du paramètre moteur de la pompe à vide secondaire 3 reste inférieure un deuxième seuil prédéfini au-delà d'une deuxième durée prédéterminée, par exemple 2 kW pendant quelques minutes, on peut contrôler la vitesse de rotation de la pompe à vide secondaire 3 à une vitesse de rotation fixe réduite (dite de « standby » en anglais), inférieure à la vitesse maximale 70Hz, de manière à limiter la consommation électrique.At very low pressure (beyond t3), for example while waiting for the airlock to open towards the process chamber for transferring the substrate, if the value of the motor parameter of the
Claims (12)
- Method for reducing the pressure in a load lock for a substrate at atmospheric pressure using a pump unit (1) having a rough-vacuum pump (2) and a high-vacuum pump (3) arranged upstream of said rough-vacuum pump (2) in the direction of flow of the gases being pumped, characterized in that, during the pressure drop and until the pressure in the load lock reaches a predefined low-pressure threshold, the rotational speed of the high-vacuum pump (3) is controlled as a function of an operating parameter of the high-vacuum pump (3) to increase the flow rate (SoR) generated by the high-vacuum pump such that the flow rate (SoR) generated by the high-vacuum pump remains within a range in which the upper value is six times the flow rate (Sol) generated by the rough-vacuum pump and the lower value is 1.3 times the flow rate (Sol) generated by the rough-vacuum pump.
- Pressure reduction method according to claim 1, characterized in that the operating parameter of the high-vacuum pump (3) is a parameter of the motor (7) of the high-vacuum pump (3).
- Pressure reduction method according to either of the preceding claims, characterized in that control of the rotational speed of the high-vacuum pump (3) is started as a function of an operating parameter of the high-vacuum pump (3) when it is detected that the value of an operating parameter of the high-vacuum pump (3) has passed a predetermined trigger threshold for a first predetermined time.
- Pressure reduction method according to one of the preceding claims, characterized in that if the value of an operating parameter of the high-vacuum pump (3) is greater than a predetermined safety threshold for longer than a second predetermined time, the rotational speed of the high-vacuum pump (3) is forced to drop.
- Pressure reduction method according to one of the preceding claims, characterized in that if the value of an operating parameter of the high-vacuum pump (3) is less than a predetermined waiting threshold for longer than a third predetermined time, the rotational speed of the high-vacuum pump (3) is set to a standby rotational speed.
- Pump unit including a rough-vacuum pump (2) and a high-vacuum pump (3), said high-vacuum pump (3) being arranged upstream of said rough-vacuum pump (2) in the direction of flow of the gases being pumped and having a variable-frequency drive (8), characterized in that the high-vacuum pump (3) includes a control unit (9) that is linked to the variable-frequency drive (8) and that is configured to control the rotational speed of the high-vacuum pump (3) as a function of a signal representing an operating parameter of the high-vacuum pump (3), such that during the pressure drop and until the pressure in the load lock reaches a predefined low-pressure threshold, the flow rate (SoR) generated by the high-vacuum pump is increased to fall within a range in which the upper value is six times the flow rate (Sol) generated by the rough-vacuum pump and the lower value is 1.3 times the flow rate (Sol) generated by the rough-vacuum pump.
- Pump unit according to Claim 6, characterized in that the rough-vacuum pump (2) includes a relief module for a pumping stage (T1, T2).
- Pump unit according to either of Claims 6 and 7, characterized in that the signal representing an operating parameter of the high-vacuum pump (3) is a parameter of the motor (7) of the high-vacuum pump (3).
- Pump unit according to Claim 8, characterized in that the parameter of the motor (7) of the high-vacuum pump (3) is current.
- Pump unit according to Claim 8, characterized in that the parameter of the motor (7) of the high-vacuum pump (3) is power.
- Pump unit according to one of Claims 6 to 10, characterized in that it has a bypass duct (10) connecting the inlet (4) of the rough-vacuum pump (2) to the inlet (11) of the high-vacuum pump (3), the bypass duct (10) having a discharge module designed to open when the suction pressure (P1) of the rough-vacuum pump exceeds the suction pressure (Pasp) of the high-vacuum pump by a predetermined excess value (ΔP) of between 100 and 400 mbar.
- Pump unit according to one of Claims 6 to 11, characterized in that the high-vacuum pump (3) is a Roots vacuum pump.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FR1656782A FR3054005B1 (en) | 2016-07-13 | 2016-07-13 | METHOD OF PRESSURE DESCENT IN A LOADING AND UNLOADING SAS AND ASSOCIATED PUMP GROUP |
PCT/EP2017/066178 WO2018010970A1 (en) | 2016-07-13 | 2017-06-29 | Method for lowering the pressure in a loading and unloading lock and associated pumping unit |
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EP3485168A1 EP3485168A1 (en) | 2019-05-22 |
EP3485168B1 true EP3485168B1 (en) | 2020-04-22 |
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EP17735085.7A Active EP3485168B1 (en) | 2016-07-13 | 2017-06-29 | Method for lowering the pressure in a loading and unloading lock and associated pumping unit |
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EP (1) | EP3485168B1 (en) |
KR (1) | KR102404612B1 (en) |
CN (1) | CN109477485B (en) |
FR (1) | FR3054005B1 (en) |
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IT201800021148A1 (en) * | 2018-12-27 | 2020-06-27 | D V P Vacuum Tech S P A | VOLUMETRIC AUXILIARY PUMP FOR VACUUM GENERATION. |
FR3098869B1 (en) | 2019-07-17 | 2021-07-16 | Pfeiffer Vacuum | Pumping group |
BE1028087B1 (en) * | 2020-02-24 | 2021-09-21 | Atlas Copco Airpower Nv | Method for controlling a vacuum system and vacuum system |
BE1028135B1 (en) * | 2020-03-10 | 2021-10-11 | Atlas Copco Airpower Nv | Method and apparatus for controlling the pump speed, computer program and a computer readable medium on which the computer program is stored thereto applied and a pump |
FR3112171B1 (en) * | 2020-10-16 | 2022-07-08 | Pfeiffer Vacuum | Method for controlling an operating power of a vacuum pump and vacuum pump |
FR3129992B1 (en) * | 2021-12-08 | 2023-12-01 | Pfeiffer Vacuum | Pumping group, pumping and treatment device and method |
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DE3639512A1 (en) * | 1986-11-20 | 1988-06-01 | Alcatel Hochvakuumtechnik Gmbh | Vacuum pump system with a Roots pump |
JP4218756B2 (en) * | 2003-10-17 | 2009-02-04 | 株式会社荏原製作所 | Vacuum exhaust device |
JP2006342688A (en) * | 2005-06-07 | 2006-12-21 | Ebara Corp | Evacuation system |
FR2888894A1 (en) * | 2005-07-20 | 2007-01-26 | Alcatel Sa | QUICK PUMPING OF ENCLOSURE WITH ENERGY SAVING |
FR2940322B1 (en) * | 2008-12-19 | 2011-02-11 | Alcatel Lucent | PRESSURE DESCENT METHOD IN LOADING AND UNLOADING SAS AND EQUIPMENT THEREFOR |
FR2952683B1 (en) * | 2009-11-18 | 2011-11-04 | Alcatel Lucent | METHOD AND APPARATUS FOR PUMPING WITH REDUCED ENERGY CONSUMPTION |
DE112012001192B4 (en) * | 2011-03-11 | 2016-12-15 | Ulvac Kiko, Inc. | Vacuum pump, vacuum pumping device and method of operating a vacuum pump |
CN104302922B (en) * | 2012-06-28 | 2017-08-08 | 斯特林工业咨询有限公司 | Pump installation and method for emptying chamber |
FR3017425A1 (en) * | 2014-02-12 | 2015-08-14 | Adixen Vacuum Products | PUMPING SYSTEM AND PRESSING DESCENT METHOD IN LOADING AND UNLOADING SAS |
-
2016
- 2016-07-13 FR FR1656782A patent/FR3054005B1/en not_active Expired - Fee Related
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2017
- 2017-06-21 TW TW106120787A patent/TWI723186B/en active
- 2017-06-29 CN CN201780042978.6A patent/CN109477485B/en active Active
- 2017-06-29 EP EP17735085.7A patent/EP3485168B1/en active Active
- 2017-06-29 WO PCT/EP2017/066178 patent/WO2018010970A1/en unknown
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FR3054005B1 (en) | 2018-08-24 |
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FR3054005A1 (en) | 2018-01-19 |
WO2018010970A1 (en) | 2018-01-18 |
KR102404612B1 (en) | 2022-05-31 |
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EP3485168A1 (en) | 2019-05-22 |
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