KR102229080B1 - Pumping system and method for lowering the pressure in a load-lock chamber - Google Patents

Abstract

The present invention is a pumping system intended to be connected to the chamber 2 of the load lock for loading and unloading a substrate, comprising a first main pumping unit 9a, 9b having at least a first maximum pumping speed S1 and a second 2 It includes a second main pumping unit (10a, 10b) with a maximum pumping speed (S2), each main pumping unit (9a, 9b, 10a, 10b) is a single-stage Roots vacuum pump (15) and a main vacuum A pump 13, wherein the single-stage Roots vacuum pump 15 is mounted in series with and upstream of the main vacuum pump 13 in the flow direction of the gases to be pumped, and the first and second main pumping units (9a, 9b, 10a, 10b) is mounted in parallel and is configured to simultaneously pump the chamber (2) of the load lock for loading and unloading the substrate, wherein the first main pumping unit ( 9a, 9b) have different pumping characteristics with respect to the second main pumping units 10a, 10b, and the first maximum pumping speed and the first maximum pumping speed of the first and second main pumping units 9a, 9b, 10a, 10b 2 It relates to a pumping system, characterized in that the difference between the maximum pumping speeds ^{exceeds 500 m 3 /h.} The invention also relates to a method of lowering the pressure in the chamber 2 of the load lock.

Description

Pumping system and method to lower the pressure in the load lock chamber {PUMPING SYSTEM AND METHOD FOR LOWERING THE PRESSURE IN A LOAD-LOCK CHAMBER}

The present invention provides a pumping system for lowering the pressure in a load lock for a substrate, such as a flat panel display or photovoltaic substrate, to a lower pressure for loading and unloading a substrate from atmospheric pressure in a processing chamber maintained at a low pressure, and It's about the method.

In certain manufacturing processes, an important step involves processing the substrate in a controlled low pressure atmosphere within the processing chamber. To maintain acceptable throughput and to avoid the presence of impurities and contaminants, the atmosphere around the substrate is first lowered to a low pressure in the load lock that is in communication with the processing chamber.

To do this, the lock has a sealed chamber, with a first door connecting the interior of the chamber with a zone of atmospheric pressure, such as a clean room, for loading at least one substrate. The chamber of the lock is connected to a pump unit that is designed to lower the pressure in the chamber to a suitable low pressure similar to the pressure inside the processing chamber to enable the substrate to be transferred to the processing chamber. The lock also has a second door for unloading the substrate into the processing chamber following evacuation. These locks are generally also used to increase the pressure of the substrate after it has been processed and unloaded at atmospheric pressure.

However, each time the substrate is loaded, the pressure inside the chamber of the lock needs to fall alternately and repeatedly within a relatively short period of time and then rise to achieve the required low pressure. This constraint is relatively harder to accommodate for larger substrates. This is particularly true for the manufacture of panel displays and photovoltaic substrates, where the chamber of the lock is necessarily large enough to accommodate one or more flat panels. For example, currently, chambers of locks used to manufacture flat panels generally have a volume of approximately 500 to 1000 liters, and in some cases greater than 5000 liters, and as a result pumping will be carried out as quickly as possible. There is a need.

Since the pressure in the chamber needs to be lowered from high to low pressure, the pumping system needs to be efficient at both high and low pressures, in order to limit the pumping time required to reach the desired low pressure. This goal will be difficult to achieve, as it requires vacuum-pump properties that are theoretically contradictory.

In fact, when pumping is started, the rotational speed of the rotors of the vacuum pump is generally lowered temporarily to enable the overpressure caused by the high pressure pump to be absorbed. Once the overpressure is released, the rotation can be accelerated until the pump operates at its maximum performance level. Low-inertia pumps are preferred for this reason, as the low-inertia pump facilitates the initial rotation and re-acceleration after the slow phase. Low-inertia pumps are generally small and have a relatively low volumetric flow rate. In addition, the pumping performance of low-inertia pumps is limited and may not be able to enable the desired low pressure to be reached within the allotted time.

Furthermore, in some cases, a gas flow is injected between the pump and the chamber of the lock, either during or after pumping. Equally, the walls of the chamber or the surfaces of the substrates may emit a non-negligible degassing flow. These additional gas flows, particularly constraining at low pressures, make it desirable to use pumps with high pumping capacity at low pressures. Importantly, such pumps are large. However, such large pumps generally have a high inertia, which makes pumping relatively inefficient when starting at high and medium pressures.

One of the objects of the present invention is to propose a pumping system and method for lowering the pressure in the load lock, which at least partially overcomes the disadvantages of the prior art at low cost.

To this end, the present invention is a pumping system designed to be connected to a chamber of a load lock for a substrate, comprising at least a first main pumping unit having a first maximum pumping speed and a second main pumping unit having a second maximum pumping speed. Wherein each main pumping unit comprises a single-stage Roots vacuum pump and a main vacuum pump, the single-stage Roots vacuum pump being arranged in series with and upstream of the main vacuum pump in the flow direction of the gases to be pumped, In a pumping system wherein the first and second main pumping units are mounted in parallel and are designed to simultaneously pump the chambers of the load lock of the substrate, the first main pumping unit is a different pumping unit than the second main pumping unit. Characterized in that the difference between the first maximum pumping speed and the second maximum pumping speed ^{exceeds 500 m 3} /h.

The present invention is also a pumping system designed to be connected to a chamber of a load lock for a substrate, comprising at least a first main vacuum pump having a first maximum pumping rate and a second main vacuum pump having a second maximum pumping rate, , The first and second main vacuum pumps are assembled in parallel and are designed to simultaneously pump the chambers of the load lock of the substrate, wherein the first main vacuum pump is different from the second main vacuum pump. It relates to a pumping system having a pumping characteristic, wherein the difference between the first maximum pumping speed and the second maximum pumping speed ^{exceeds 500 m 3 /h.}

By using a first main vacuum pumping device, such as a high inertia main pumping unit or a main vacuum pump, in parallel with a second main vacuum pumping device, such as a main pumping unit or a main vacuum pump with low inertia, pumping is achieved. At the start, the rotation of the rotors of the two main vacuum pumping devices is slowed down to enable the overpressure created by high pressure pumping to be absorbed. Once the overpressure is released, the low-inertia main vacuum pumping device can be reaccelerated faster than the high-inertia main vacuum pumping device in order to reach maximum speed. The acceleration of the rotation of the high-inertia main vacuum pumping device is slower, but allows a significant volumetric flow rate to be achieved at lower pressures in order to reach the desired pressure within the allotted time. The pumping system thereby benefits from the advantages of each pumping device to quickly achieve the desired pressure at a limited cost and compensates for the disadvantages of each pumping device.

According to one embodiment, the first maximum pumping speed provided by the "high-inertia main vacuum pumping device" is 2000 m ³ /h or more, and the second maximum pumping speed provided by the "low-inertia main vacuum pumping device" Is less than 2000 m ³ /h.

For example, the difference between the first maximum pumping speed and the second maximum pumping speed is between 500 and 3500 m ³ /h. The difference in pumping speed is thus large enough to ensure that the first main vacuum pumping device is more efficient than the second main vacuum pumping device at low pressure and vice versa at high pressure.

According to an exemplary embodiment, the pumping system has at least two main vacuum pumps or at least two main pumping units having substantially the same pumping characteristics.

The present invention is also a method of lowering the pressure in the chamber of the load lock using the pumping system described above, wherein the chamber of the load lock of the substrate comprises at least one first main pumping unit and a first having a first maximum pumping speed. 2 pumped simultaneously using a second main pumping unit having a maximum pumping speed, the main pumping units are arranged in parallel and have different pumping characteristics, the first maximum pumping speed and the second maximum pumping of the main pumping units It relates to a method for lowering the pressure, characterized in that the difference between the speeds ^{exceeds 500 m 3 /h.}

The present invention is also a method for lowering the pressure in the chamber of the load lock using the pumping system described above, wherein the chamber of the load lock of the substrate comprises at least one first main vacuum pump having a first maximum pumping speed and a first 2 pumped simultaneously using a second main vacuum pump having a maximum pumping speed, the main vacuum pumps are arranged in parallel and have different pumping characteristics, the first maximum pumping speed and the second maximum pumping of the main vacuum pumps It relates to a method for lowering the pressure, characterized in that the difference between the speeds ^{exceeds 500 m 3 /h.}

Other features and advantages of the invention are provided in the following description, which is provided as a non-limiting example with reference to the accompanying drawings.
1 is a schematic diagram of a first exemplary pumping system connected to a chamber of a load lock,
2 shows the pumping speed of the first main pumping unit as a function of pressure (curve A, mbar) (m ³ /h) and the pumping speed of the second main pumping unit as a function of pressure (curve B, mbar) (m ³⁾ /h),
3 is a graph showing the pressure reduction curve (mbar) as a function of time (in seconds) in the chamber of the load lock for different pumping layouts, and
4 is a schematic diagram of a second exemplary pumping system connected to the chamber of the load lock.
In these figures, like elements are indicated using like reference numerals.

1 shows a first exemplary pumping system 1 connected to a chamber 2 of a load lock.

In a known manner, the chamber 2 of the load lock is a device that connects the interior of the chamber 2 with a zone of atmospheric pressure, such as a clean room, for loading at least one large substrate, such as a flat panel display or photovoltaic substrate. 1 has a door (4). Such chambers generally have a volume of between 500 and 5000 liters. The chamber 2 also restores the chamber 2 to atmospheric pressure, in particular after the substrate 5 has been transferred, as well as a second door 6 for unloading the substrate into the processing chamber 7 following evacuation. It is provided with a device (8) for injecting an inert gas.

The pumping system 1 has at least one first main vacuum pumping device and one second main vacuum pumping device, arranged in parallel and designed to pump from the chamber 2 at the same time.

The "main vacuum pumping device" is a positive displacement pumping in which the gas to be pumped is sucked in, compressed and then released, in ^{order to achieve a primary vacuum, i.e. to achieve a pressure between 10 2} and 10 ^{-1 Pa.} It is a device. The main vacuum pumping device, unlike the turbomolecular pumping device, can operate from atmospheric pressure.

The main vacuum pumping device may be a main vacuum pump 13a, 13b, 14a, 14b (Fig. 4) or a main pumping unit 9a, 10a, 9b, 10b (Fig. 1).

The main pumping units 9a, 10a, 9b, 10b include a single-stage Roots vacuum pump 15 and a main vacuum pump 13, and the single-stage Roots vacuum pump 15 is It is arranged in series with and upstream of the main vacuum pump 13 in the direction (arrow'G' in Fig. 1).

The single-stage Roots vacuum pump 15 is a turbomolecular vacuum pump, since the single-stage Roots vacuum pump 15 can only produce a primary vacuum, i.e. a low pressure between ^{10 2} and 10 ^{-1 Pa.} no.

The parallel arrangement of the main pumping units 9a, 10a, 9b, 10b makes it possible to isolate the main pumping units 9a, 10a, 9b, 10b, in particular to increase the atmospheric pressure in the chamber 2, It is provided by connecting the individual inlets of the main pumping units 9a, 10a, 9b, 10b to the chamber 2 using a vacuum piping 11 comprising an isolation valve 12.

This assembly means that when the pressure is reduced, the gas to be pumped coming from the chamber 2 flows simultaneously and in parallel through all the main pumping units 9a, 10a, 9b, 10b.

Furthermore, the vacuum piping 11 has substantially the same conductivity between the chamber 2 and the individual inlets of the main pumping units 9a, 10a, 9b, 10b during pressure reduction. The vacuum piping 11 in particular does not have soft-pumping devices.

In the example shown in Fig. 1, the pumping system 1 has four main pumping units 9a, 10a, 9b, 10b.

As suggested above, the main pumping units 9a, 10a, 9b, 10b include a main vacuum pump 13 and a single-stage Roots vacuum pump 15, and the single-stage Roots vacuum pump 15 Is arranged in series with and upstream of the main vacuum pump 13 in the flow direction of the gases being pumped.

The main vacuum pump 13 is, for example, a multistage dry vacuum pump, ie a pump comprising several pumping stages assembled in series one after the other and fluidly connected in series in turn by interstage channels. The interstage channels connect between the suction and associated discharge of the main vacuum pump 13 with the inlet of the stage following the outlet of the preceding pumping stage.

The interior of the main vacuum pump 13 has two rotors with the same contour, rotating in opposite directions inside the sheets. During rotation, the aspirated gas is trapped in the free space between the rotor and stator before being discharged to the subsequent pumping stage. The rotors are supported on shafts, which extend through the pumping stages and are driven by a motor of the main vacuum pump 13. The pumping stages are rigidly connected together to form a unitary pumping member through which the shafts of the rotors pass through themselves. The main vacuum pump 13 is, for example, a rotary lobe pump such as a Roots pump or a similar pump such as a claw pump.

In general, a rotary lobe Roots vacuum pump has two rotors of the same contour, which extend through the pumping stages and are driven rotationally in opposite directions by a motor inside the stator. During rotation, the inhaled gas is trapped in the free space between the rotors and the stator before being released. The pump operates without mechanical contact between the stator and the rotors of the main vacuum pump, which completely eliminates the need for oil in the pumping stages.

The single-stage Roots vacuum pump 15 is a main vacuum pump 13 in that it has only one pumping stage and requires the use of a main vacuum pump 13 connected in series in the same discharge path. It is different from Like the main vacuum pump 13, it is a positive displacement vacuum pump, ie a pump that uses rotors to suck in, deliver and then discharge the gas to be pumped.

The single-stage Roots vacuum pump 15 has its own motor, which is designed to rotationally drive the rotor in its single pumping stage.

Consequently, the pumping stage of the multi-stage main vacuum pump cannot be considered to be a single-stage Roots vacuum pump for the purposes of the present invention.

In addition, at least one first main pumping unit and at least one second main pumping unit 9a, 10a, 9b, 10b have different pumping characteristics.

In the example shown in Fig. 1, the two first main pumping units 9a, 9b have different pumping characteristics than the two second main pumping units 10a, 10b.

The pumping properties are generally defined by the distribution of pumping rates as a function of pressure, as shown by curves A and B in FIG. 2. This distribution is usually provided by the manufacturer.

^{The first main pumping unit 9a has a first maximum pumping speed, for example 2000 m 3} /h or higher, provided by the "high-inertia main vacuum pumping device", and the second main pumping unit 10a Has a second maximum pumping speed, which is less than ^{2000 m 3} /h, provided by the "low-inertia main vacuum pumping device".

Furthermore, the difference between the first maximum pumping speed S1 of the first main pumping units 9a, 9b and the second maximum pumping speed S2 of the second main pumping units 10a, 10b is 500 m ³ / greater than h, for example ^{between 500 and 3500 m 3} /h. The difference between the main pumping units is thus large enough so that the first main pumping units 9a, 9b are more efficient than the second main pumping units 10a, 10b at low pressures and vice versa at high pressures.

For example, as shown by curve A in FIG. 2, the first maximum pumping speed S1 of the two first main pumping units 9a, 9b is at a pressure of approximately 0.35 mbar (or 35 Pa). About 2600 m ³ /h.

The second maximum pumping speed S2 of the two second main pumping units 10a, 10b is approximately 1700 m ³ /h for a corresponding pressure of approximately 0.5 mbar (or 50 Pa).

Considering the large pumping capacity of the first main pumping units 9a, 9b, the main pumping units are larger and have a greater inertia than the second main pumping units 10a, 10b.

In this way, by using two first high-inertia main pumping units 9a, 9b in parallel with two second low-inertia main pumping units 10a, 10b, four single-stage Roots vacuum pumps ( The rotation of the rotors of 15) is slowed to enable absorption of the overpressure generated by high pressure pumping. Once the overpressure is released, the single-stage Roots vacuum pumps 15 of the two second low-inertia main pumping units 10a, 10b, in order to reach the maximum speed, the two first high-inertia main pumping units. It can be re-accelerated more quickly than the unit's single-stage Roots vacuum pumps 15. The acceleration of the rotation of the two single-stage Roots vacuum pumps 15 of the first high-inertia main pumping units 9a, 9b is slower, but allows a significant volumetric flow rate to reach the desired pressure within the allotted time. For this reason, it makes it possible to achieve at low pressure. The pumping system 1 thereby benefits from the advantages of each pumping device in order to quickly achieve the desired pressure at a limited cost and compensates for the disadvantages of each pumping device.

Curves showing pressure reduction as a function of time in FIG. 3 in the chamber of a 1000 liter load lock for different pumping arrangements are discussed below. In this example, a pressure of 0.025 mbar needs to be reached within 23.5 seconds from atmospheric pressure (approximately 1000 mbar). This constraint is illustrated by point O in FIG. 3.

Curve C shows the decrease in pressure as a function of time for two first high-inertia main pumping units 9a, which have the same pumping characteristics and are assembled in parallel. A pressure of 0.025 mbar is achieved in approximately 24 seconds.

Curve D represents the decrease in pressure as a function of time for the first main pumping unit 9a and the second main pumping unit 10b, which have different pumping properties and are assembled in parallel. The desired pressure of 0.025 mbar is achieved in 23 seconds, within the allotted time.

Curve E shows the decrease in pressure as a function of time for two second low-inertia main pumping units 10a, which have the same pumping characteristics and are assembled in parallel. According to this arrangement, the desired pressure of 0.025 mbar is achieved in 27 seconds.

Curve F shows the decrease in pressure as a function of time for three first high-inertia main pumping units 9a, which have the same pumping characteristics and are assembled in parallel. A pressure of 0.025 mbar is achieved in approximately 16 seconds.

Curve G represents the decrease in pressure as a function of time for three second low-inertia main pumping units 10a, which have the same pumping characteristics and are assembled in parallel. The desired pressure of 0.025 mbar is achieved in 18 seconds.

As a result, if the main pumping units have the same pumping characteristics, the parallel assembly needs to be tripled (curve F and curve G) to achieve the required pressure of 0.025 mbar within the allotted time of 23.5 seconds.

Conversely, if the main pumping units 9a, 10a have different pumping characteristics, and are appropriately selected to combine the high-inertia main pumping unit and the low-inertia main pumping unit (curve D), the desired pressure is the allotted time Can be achieved within

Indeed, when pumping starts at high pressure, the re-acceleration of the rotational speed of the rotors after the slowdown caused by absorption of gas overpressure is slower for the first high-inertia main pumping unit. The first high-inertia main pumping unit is thus less efficient at high and medium pressures than the first low-inertia main pumping unit, but conversely enables better pumping speeds at low pressures. Conversely, the second low-inertia main pumping unit enables high pumping speeds at high pressures, but provides low performance at low pressures.

4 shows another exemplary pumping system 1 ′ connected to a chamber 2 of a load lock for a substrate 5.

The pumping system 1'has at least one first main vacuum pump 13a, 13b having a first maximum pumping speed and a second main vacuum pump 14a, 14b having a second maximum pumping speed.

As described above, the main vacuum pumps 13a, 13b, 14a, 14b comprise a multistage dry vacuum pump, i.e., several pumping stages that are sequentially assembled in series, and are fluidized in series in turn by interstage channels. It may be pumps connected to. The rotors are supported on shafts, extending through the pumping stages and driven by a motor of the main vacuum pumps 13a, 13b, 14a, 14b. The pumping stages are rigidly connected together to form a unitary pumping member through which the shafts of the rotors pass through themselves. The main vacuum pumps 13a, 13b, 14a, 14b are, for example, rotary lobe pumps such as Roots pumps or similar pumps such as claw pumps. The pump can only produce a primary vacuum, i.e. a pressure as low as between 102 and 10-1 Pa.

The first and second main vacuum pumps 13a, 13b, 14a, 14b are arranged in parallel and are designed to simultaneously pump the chamber 2 of the load lock of the substrate.

At least one first main vacuum pump and one second main vacuum pump have different pumping characteristics.

In the example shown in Fig. 4, the two first main vacuum pumps 13a, 13b have different pumping characteristics than the two second main vacuum pumps 14a, 14b.

The first main vacuum pumps 13a, 13b have ^{a first maximum pumping speed, for example 2000 m 3} /h or more, and the second main vacuum pumps 14a, 14b, 2000 m ³ /h Has a second maximum pumping rate that is less than.

Furthermore, the difference between the first maximum pumping speed of the first main vacuum pumps 13a and 13b and the second maximum pumping speed of the second main vacuum pumps 14a and 14b is greater than ^{500 m 3 /h,} For example between 500 and 3500 m ³ /h.

Claims (8)

A pumping system designed to be connected to the chamber 2 of the load lock for the substrate 5, at least
-A first main pumping unit (9a, 9b) having a first maximum pumping speed (S1), and
-Comprising a second main pumping unit (10a, 10b) having a second maximum pumping speed (S2),
-Each of the main pumping units 9a, 10a, 9b, 10b includes a single-stage Roots vacuum pump 15 and a main vacuum pump 13, wherein the single-stage Roots vacuum pump 15 is pumped. Arranged in series with and upstream of the main vacuum pump 13 in the flow direction of the gases being
-Said first and second main pumping units (9a, 9b, 10a, 10b) are arranged in parallel and arranged to simultaneously pump the chamber (2) of the load lock of the substrate, in a pumping system,
-The first main pumping unit (9a, 9b) has a pumping characteristic different from the second main pumping unit (10a, 10b), the first and second main pumping units (9a, 9b, 10a, 10b) A pumping system, characterized in that the difference between the first maximum pumping speed (S1) and the second maximum pumping speed (S2) ^{of exceeds 500 m 3 /h.} A pumping system designed to be connected to the chamber 2 of the load lock for the substrate 5, with at least one first main vacuum pump 13a, 13b having a first maximum pumping speed and a second maximum pumping speed. It comprises a second main vacuum pump (14a, 14b), the first and second main vacuum pumps (13a, 13b, 14a, 14b) are assembled in parallel, and at the same time the chamber (2) of the load lock of the substrate. In the pumping system that is designed to pump,
The first main vacuum pump (13a, 13b) has a pumping characteristic different from the second main vacuum pump (14a, 14b), the difference between the first maximum pumping speed and the second maximum pumping speed is 500 m Pumping system, characterized in that it exceeds ^{3 / h.} The method according to claim 1 or 2,
The first maximum pumping speed (S1) is 2000 m ³ /h or more and the second maximum pumping speed (S2) is ^{less than 2000 m 3} /h. The method according to claim 1 or 2,
A pumping system, characterized in that the difference between the first maximum pumping speed (S1) and the second maximum pumping speed (S2) is more ^{than 500 m 3} /h and not more than 3500 m ^{3 /h.} The method of claim 2,
A pumping system, characterized in that at least two first main vacuum pumps (13a, 13b) have the same pumping characteristics, and at least two second main vacuum pumps (14a, 14b) have the same pumping characteristics. A method of lowering the pressure in the chamber (2) of the load lock using the pumping system (1) according to claim 1, wherein
The chamber 2 of the load lock of the substrate comprises a first main pumping unit 9a, 9b having at least a first maximum pumping speed S1 and a second main pumping unit 10a having a second maximum pumping speed S2. , 10b), and the main pumping units 9a, 9b, 10a, 10b are arranged in parallel and have different pumping characteristics, the first maximum pumping speed and the second maximum pumping speed Method for lowering pressure, characterized in that the difference between ^{them exceeds 500 m 3 /h.} A method of lowering the pressure in the chamber (2) of the load lock using the pumping system (1) according to claim 2, wherein
The chamber 2 of the load lock of the substrate uses a first main vacuum pump 13a, 13b having at least a first maximum pumping speed and a second main vacuum pump 14a, 14b having a second maximum pumping speed. Pumped simultaneously, the main vacuum pumps 13a, 13b, 14a, 14b are arranged in parallel and have different pumping characteristics, and the difference between the first maximum pumping speed and the second maximum pumping speed is 500 Method for lowering the pressure, characterized in that it exceeds m ^{3 /h.} The method of claim 1,
A pumping system, characterized in that at least two first main pumping units (9a, 9b) have the same pumping characteristics, and at least two second main pumping units (10a, 10b) have the same pumping characteristics.

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