WO2015121222A1

WO2015121222A1 - Pumping system and method for lowering the pressure in a load-lock chamber

Info

Publication number: WO2015121222A1
Application number: PCT/EP2015/052698
Authority: WO
Inventors: Nicolas Becourt
Original assignee: Adixen Vacuum Products
Priority date: 2014-02-12
Filing date: 2015-02-10
Publication date: 2015-08-20
Also published as: CN105980706A; CN105980706B; EP3105455B1; EP3105455A1; KR20160122759A; FR3017425A1; KR102229080B1

Abstract

The invention concerns a pumping system intended to be connected to a load-lock chamber (2) for loading and unloading a substrate (5), comprising at least a first primary pumping unit (9a, 9b) having a first maximum pumping speed (S1) and a second primary pumping unit (10a, 10b) having a second maximum pumping speed (S2), each primary pumping unit (9a, 9b, 10a, 10b) comprising a single-stage Roots vacuum pump (15) and a primary vacuum pump (13), the single-stage Roots vacuum pump (15) being mounted in series with and upstream from the primary vacuum pump (13) in the direction of flow of the gases to be pumped, said first and second primary pumping units (9a, 9b, 10a, 10b) being mounted in parallel and configured to simultaneously pump the load-lock chamber (2) for loading and unloading the substrate, characterised in that said first primary pumping unit (9a, 9b) has different pumping characteristics to said second primary pumping unit (10a, 10b), the difference between the first and second maximum pumping speeds of said first and second primary pumping units (9a, 9b, 10a, 10b) being greater than 500 m³/h. The invention also concerns a method for lowering the pressure in a load-lock chamber (2).

Description

Pumping system and method of descent pressure in a loading and unloading chamber

The present invention relates to a pumping system and a method of descent in pressure in a lock of 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 a low pressure for the loading and unloading of the substrate in a treatment chamber maintained at low pressure.

In some manufacturing processes, an important step is to treat a low pressure controlled atmosphere substrate in a process chamber. To maintain an acceptable rate and to avoid the presence of any impurity and pollution, the atmosphere surrounding the substrate is first lowered at low pressure in a loading chamber and unloading communicating with the treatment chamber.

For this, the airlock comprises a sealed chamber, a first door communicates the interior of the chamber with an atmospheric pressure zone, such as a clean room, for loading at least one substrate. The chamber of the chamber is connected to a pumping unit for lowering the pressure in the chamber until a suitable low pressure is reached similar to that prevailing in the treatment chamber so as to transfer the substrate to the treatment chamber . The airlock further includes a second door for unloading the substrate into the treatment chamber after being evacuated. This same airlock is generally also used for the rise in pressure of the substrate at the end of its treatment, and its discharge at atmospheric pressure.

It will be understood, however, that each loading of substrates necessitates lowering and then alternately raising the pressure in the enclosure of the airlock in a relatively short time to reach the desired low pressure. This constraint is even more difficult to respect for large substrates. This is particularly the case for the manufacture of flat displays or photovoltaic substrates, the chamber of the chamber necessarily having the appropriate volume to contain one or more flat screens. For example, at present, the enclosures of airlock used for the manufacture of flat screens have volumes generally of the order of 500 to 1000 liters, sometimes exceeding 5000 liters, which must therefore be pumped as quickly as possible.

Since it is a question of lowering the pressure in the chamber from a high pressure to a low pressure, the pumping solution must perform well at high or low pressure in order to limit the pumping time to the desired low pressure. This goal can be difficult to achieve because it uses characteristics of vacuum pumps a priori antagonistic.

In fact, at the beginning of the pumping, the rotors of the vacuum pumps generally undergo a temporary slowing down of the speed of rotation, allowing the absorption of the overload caused by the pumping at high pressure. Once the excess charge is removed, the rotation can accelerate until the maximum performance of the pump is reached. Pumps of low inertia are therefore preferred, which facilitates their rotation and re-acceleration after the deceleration phase. Pumps of low inertia are generally small and have a relatively low volumetric flow rate. Also, the pumping performance of low inertia pumps are limited and may not achieve the desired low pressures within the time limit.

In addition, in some cases, a gas flow is injected between the chamber of the lock chamber and the pump during or at the end of the pumping. Also, the walls of the enclosure or the surfaces of the substrates can release a non-negligible degassing flow. These additional gas flows that are binding especially low pressure, it is then preferable to use pumps with high pumping capacity at low pressure, including large dimensions. However, these large pumps generally have a high inertia, which makes them relatively inefficient at the beginning of pumping at high and medium pressure.

One of the aims of the present invention is to propose a pumping system and a pressure descent method in a loading and unloading chamber, which solve the disadvantages of the state of the art at a lower cost and at least in part.

For this purpose, the subject of the invention is a pumping system intended to be connected to a chamber for loading and unloading a substrate, comprising at least a first primary pumping group having a first maximum pumping speed and a second primary pumping unit having a second maximum pumping rate, each primary pumping unit comprising a single-stage Roots vacuum pump and a primary vacuum pump, the single-stage Roots vacuum pump being mounted in series and upstream of the pumping pump. primary vacuum in the flow direction of the gases to be pumped, said first and second primary pumping groups being connected in parallel and configured to simultaneously pump the enclosure of the loading and unloading chamber of the substrate, characterized in that said first group primary pumping system has pumping characteristics distinct from said second primary pumping group, the difference between the primary pumping second and second maximum pump speeds being greater than 500 m ³ / h. The invention also relates to a pumping system intended to be connected to a chamber for loading and unloading a substrate, comprising at least a first primary vacuum pump having a first maximum pump speed and a second pump primary vacuum pump having a second maximum pump speed, the first and second primary vacuum pumps being connected in parallel and configured to simultaneously pump the enclosure of the loading and unloading chamber of the substrate, characterized in that the first vacuum pump primary has separate pumping characteristics of the second primary vacuum pump, the difference between the first and second maximum pump speeds being greater than 500 m ³ / h.

By using a first primary vacuum pumping device, such as a primary pumping unit or a primary vacuum pump, of high inertia in parallel with a second primary vacuum pumping device, such as a primary pumping unit or a primary vacuum pump, of low inertia, at the beginning of the pumping, the rotation of the rotors of the two pumping devices in primary vacuum will slow down to allow the absorption of the overload caused by the high pressure pumping. Once the excess charge evacuated, the low-inertial primary vacuum pumping device will be able to re-accelerate faster than the high-inertia primary vacuum pumping device to reach its full speed. Acceleration of the rotation of the primary vacuum pumping device of high inertia will be slower but will achieve high volumetric flow rates at low pressure in order to meet the time limit to reach the desired pressure. The pumping system thus makes it possible to benefit from the advantages and to compensate for the weak points of each pumping device in order to quickly obtain the desired pressure, at a controlled cost.

According to an exemplary embodiment, the first maximum pumping speed is greater than or equal to 2000 m ³ / h, denoting a "high-inertia primary vacuum pumping device", and the second maximum pumping speed is less than 2000 m ³ / h , designating a "low-inertia primary vacuum pumping device".

For example, the difference between the first maximum pump speed and the second maximum pump speed is between 500 and 3500 m ³ / h. The difference between the pumping speeds is thus sufficiently large for a first primary vacuum pumping device to be more efficient than the second pumping device in primary vacuum at low pressure and reciprocally at high pressure.

According to an exemplary embodiment, the pumping system comprises at least two primary vacuum pumps or at least two primary pumping groups, having substantially identical pumping characteristics. The subject of the invention is also a method for descent in pressure in a chamber for loading and unloading by a pumping system as described above, characterized in that the chamber of loading and unloading chambers is simultaneously pumped. of the substrate by means of at least a first primary pumping group having a first maximum pumping rate and a second primary pumping group having a second maximum pumping rate, said primary pumping units being connected in parallel and having pumping, the difference between the first and the second maximum pumping rate of said primary pumping groups being greater than 500 m ³ / h.

The subject of the invention is also a method of descent in pressure in a chamber for loading and unloading by a pumping system as described above, characterized in that the chamber of loading chamber and discharging the substrate by means of at least a first primary vacuum pump having a first maximum pumping rate and a second primary vacuum pump having a second maximum pumping rate, said first and second primary vacuum pumps being connected in parallel and having distinct pumping characteristics, the difference between the first and the second maximum pumping rate of said primary vacuum pumps being greater than 500 m ³ / h.

Other features and advantages of the invention will emerge from the following description given by way of example, without limitation, with reference to the accompanying drawings, in which:

FIG. 1 represents a schematic view of a first example of a pumping system connected to an enclosure for a loading and unloading chamber, FIG. 2 is a graph showing the pumping speed (in m ³ / h). of a first primary pumping group as a function of the pressure (Curve A, in mbar) and the pumping speed (in m ³ / h) of a second primary pumping group as a function of the pressure (Curve B, in mbar), and

FIG. 3 is a graph showing pressure descent curves (in mbar) as a function of time (in seconds) in a loading and unloading chamber for different pumping configurations, and FIG. a schematic representation of a second example of a pumping system connected to the chamber of loading and unloading lock. In these figures, the identical elements bear the same reference numbers. FIG. 1 shows a first example of a pumping system 1 connected to an enclosure 2 of a loading and unloading chamber (or "load lock").

In a manner known per se, the chamber 2 of the loading and unloading chamber has a first door 4 placing the interior of the chamber 2 in communication with a zone under atmospheric pressure, such as a clean room, for loading. at least one large substrate 5, such as a flat panel display ("flat panel display" in English) or a photovoltaic substrate. Such enclosures have a volume generally between 500 and 5000 liters. The chamber 2 further comprises a second door 6 for discharging the substrate 5 into a treatment chamber 7 after evacuation, as well as a device for introducing a neutral gas 8, in particular for the return to the pressure in the chamber 2 after the transfer of the substrate 5.

The pumping system 1 comprises at least first and second primary vacuum pump devices connected in parallel, configured to simultaneously pump the chamber 2.

The term "primary vacuum pump device" designates a volumetric pumping device in which the gas to be pumped is sucked, compressed and discharged, in order to obtain a primary vacuum, that is to say to obtain a pressure of between 10 ² and 10 Pa. The primary vacuum pumping device can operate at atmospheric pressure, as opposed to a turbomolecular pumping device.

The primary vacuum pumping device may be a primary vacuum pump 13a, 13b, 14a, 14b (Figure 4) or a primary pumping group 9a, 10a, 9b, 10b (Figure 1).

A primary pumping unit 9a, 10a, 9b, 10b comprises a single-stage Roots vacuum pump 15 and a primary vacuum pump 13, the single-stage Roots vacuum pump 15 being connected in series and upstream of the primary vacuum pump 3 in the direction of flow of the gases to be pumped (arrow G in FIG. 1).

The single-stage Roots vacuum pump 5, also known as the Roots depressor, is not a turbomolecular vacuum pump because the single-stage Roots vacuum pump 5 can achieve only a primary boundary vacuum, i.e. low pressure between 0 ² and 0 Pa.

The parallel connection of the primary pumping units 9a, 0a, 9b, 10b is ensured by the connection of the respective inputs of the primary pumping groups 9a, 0a, 9b, 0b to the enclosure 2 by a vacuum line comprising a valve of isolation 2 allowing the isolation of the primary pumping groups 9a, 0a, 9b, 0b, especially for the rise at atmospheric pressure in the chamber 2. This assembly is such that during the pressure drop, the gas to be pumped from the chamber 2, circulates at the same time and in parallel through all the primary pumping groups 9a, 10a, 9b, 10b.

It is further provided that the vacuum line 11 has substantially the same conductance between the chamber 2 and the respective inlet of the primary pumping groups 9a, 10a, 9b, 10b during the pressure drop. The vacuum line 11 is in particular devoid of specific devices called slow pumping (or "soft pumping" in English).

In the example shown in FIG. 1, the pumping system 1 comprises four primary pumping groups 9a, 10a, 9b, 10b.

As mentioned above, a primary pumping unit 9a, 10a, 9b, 10b comprises a primary vacuum pump 13 and a single-stage Roots vacuum pump 15, the single-stage Roots vacuum pump 15 being connected in series and upstream of the pump. primary vacuum 13 in the flow direction of the gases to be pumped.

The primary vacuum pump 13 is for example a multi-stage dry vacuum pump, that is to say having several pumping stages connected in series one after the other, and fluidly connected in series one after the other. others by interstage channels. The inter-stage channels connect the output of the preceding pump stage to the input of the next stage, between a suction of the primary vacuum pump 13 and its discharge.

Inside, the primary vacuum pump 13 comprises two rotors of identical profiles, rotating in the housing in opposite directions. During the rotation, the sucked gas is trapped in the free space between the rotors and the stator, then it is pumped to the next pumping stage. The rotors are carried by shafts extending into the pumping stages and are driven by a motor of the primary vacuum pump 13. The pumping stages are joined together to form a monobloc pump body, traversed by the shafts of the pumps. rotors. The primary vacuum pump 3 is for example rotary lobes such as Roots type or a similar principle, such as Claw type.

In general, a rotary lobe vacuum pump "Roots" comprises two rotors of identical profiles, carried by two shafts extending in the pumping stages and driven by a motor to rotate inside a stator in sense opposite. During the rotation, the sucked gas is trapped in the free space between the rotors and the stator, then it is repressed. The operation is carried out without any mechanical contact between the rotors and the stator of the primary vacuum pump, which allows the total absence of oil in the pumping stages.

The single-stage Roots vacuum pump 5 differs from the primary vacuum pump 3 in that it has only one pumping stage and requires the use of a vacuum pump. primary 13 connected in series to its discharge. It is, like the primary vacuum pump 13, a volumetric vacuum pump, that is to say which, with the aid of rotors sucks, transfers and then delivers the gas to be pumped.

A single-stage Roots vacuum pump 15 comprises a clean motor adapted to drive rotors in rotation in its single pumping stage.

Thus, a pumping stage of a multi-stage primary vacuum pump can not be considered as a single-stage Roots vacuum pump within the meaning of the present invention.

In addition, at least one first and at least one second primary pumping groups 9a, 10a, 9b, 10b have distinct pumping characteristics.

In the example represented in FIG. 1, the first two primary pumping groups 9a,

9b show distinct pumping characteristics of the two second primary pumping groups 10a, 10b.

The pumping characteristics are generally defined by the distribution of the pumping speeds as a function of pressure as represented by the curves A and B in FIG. 2. This distribution is generally a data item of the manufacturer.

The first primary pumping group 9a has a first maximum pumping speed, for example greater than or equal to 2000m ³ / h, denoting a "high-inertia primary vacuum pumping device", and the second primary pumping group 0a has a second maximum pumping rate less than 2000m ³ / h, denoting a "low inertia primary vacuum pumping device".

In addition, the difference between the first maximum pumping speed S of the first primary pumping group 9a, 9b and the second maximum pumping rate S2 of the second primary pumping group 0a, 0b is greater than 500 m ³ / h, as between 500 and 3500 m ³ / h. The difference between the primary pumping groups is thus large enough for a first primary pumping group 9a, 9b to be more efficient than the second primary pumping group 0a, 0b at low pressure and reciprocally at high pressure.

For example, and as represented on the curve A of FIG. 2, the first maximum pumping speed S of the two first primary pumping groups 9a, 9b is of the order of 2600m ³ / h for a corresponding pressure of the order 0.3 mbar (or 35 Pa).

The second maximum pumping rate S2 of the two second primary pumping groups 0a, 0b is of the order of 700 m ³ / h for a corresponding pressure of the order of 0.5 mbar (or 50 Pa). Because of their large pumping capacities, the first primary pumping groups 9a, 9b have a greater dimensioning and inertia than the second primary pumping groups 10a, 10b.

By thus using two first primary pumping groups 9a, 9b of high inertia in parallel with two second primary pumping groups 10a, 10b of low inertia, rotation of the rotors of the four single-stage Roots vacuum pumps 15 will slow down to allow absorption. overload caused by high pressure pumping. Once the excess charge has been removed, the single-stage Roots vacuum pumps 15 of the two second low-inertia primary pumping units 10a, 10b will be able to re-accelerate faster than the single-stage Roots vacuum pumps 15 of the first two groups of primary pumping of high inertia to reach their full regime. The acceleration of the rotation of the two single-stage Roots vacuum pumps 15 of the first primary pumping groups 9a, 9b of high inertia will be slower but will allow high volumetric flow rates to be reached at low pressure in order to be able to respect the time allowed to reach the desired pressure. The pumping system 1 thus makes it possible to benefit from the advantages and to compensate for the weak points of each pumping device in order to quickly obtain the desired pressure, at a controlled cost.

Reference is now made to the pressure-descent curves as a function of time in FIG. 3, in a 1000 liter loading and unloading chamber for different pumping configurations. In this example, a pressure of 0.025mbar must be reached in 23.5 seconds from atmospheric pressure (about 1000Ombars). This constraint is illustrated by the point O in FIG.

Curve C represents the pressure drop versus time curve for two first primary pumping groups 9a of high inertia having identical pumping characteristics, mounted in parallel. It is found that a pressure of 0.025 mbar is reached at about 24 seconds.

Curve D represents the pressure drop versus time curve for first and second primary pumping groups 9a, 10b having distinct pumping characteristics, respectively of high and low inertia, connected in parallel. The desired pressure is reached from 0.025 mbar to 23 seconds, within the specified time.

Curve E represents the pressure drop versus time curve for two second low inertia primary pumping groups 10a having identical pumping characteristics, connected in parallel. It can be seen with this configuration that the desired pressure of 0.025 mbar is reached after 27 seconds. Curve F represents the pressure drop versus time curve for three first primary pumping groups 9a of high inertia having identical pumping characteristics, connected in parallel. It is found that a pressure of 0.025 mbar is reached in about 16 seconds.

Curve G represents the pressure drop versus time curve for three second low inertia primary pumping groups 10a having identical pumping characteristics, connected in parallel. It is found that the desired pressure of 0.025 mbar is reached after 18 seconds.

Therefore, with primary pumping units with identical pumping characteristics, it is necessary to triple the parallel assembly to meet the pressure constraint of 0.025mbar within the allowed time of 23.5 seconds (curves F and G).

On the other hand, with primary pumping units 9a, 10a having distinct pumping characteristics, suitably selected to combine high and low inertia primary pumping units (curve D), the desired pressure can be achieved within the time period. time.

Indeed, at the beginning of the pumping, at high pressure, the re-acceleration of the speed of rotation of the rotors after the slowdown due to the absorption of gas overload, is slower for the first primary pumping group with high inertia. The first primary pumping group with high inertia thus has a lower efficiency at high and medium pressure than the second primary low inertia pumping group but allows on the other hand to obtain a better pumping speed at low pressure. Conversely, the second primary low-inertia pumping group makes it possible to obtain a high pumping speed at high pressure but gives low performance at low pressure.

FIG. 4 shows another example of a pumping system 1 'connected to an enclosure 2 for an airlock for loading and unloading a substrate 5.

The pumping system V comprises at least a first primary vacuum pump 13a, 13b having a first maximum pumping rate and a second primary vacuum pump 4a, 4b having a second maximum pumping speed.

As previously described, the primary vacuum pumps 3a, 3b, 4a, 14b may be multi-stage dry vacuum pumps, that is to say having several pumping stages connected in series one after the other, and fluidly connected. in series one after the other by the inter-floor channels. The rotors are carried by shafts extending into the pumping stages and are driven by a motor of the primary vacuum pump 3a, 13b, 14a, 14b. The pumping stages are joined together to form a one-piece pump body, crossed by the trees of the rotors. The primary vacuum pump 13a, 13b, 14a, 14b is for example rotary lobes such as Roots type or a similar principle, such as Claw type. It can only reach a primary limit vacuum, that is to say a low pressure between 0 ² and 0 ¹ Pa.

The first and second primary vacuum pumps 13a, 3b, 14a, 14b are connected in parallel and configured to simultaneously pump the chamber 2 of the loading and unloading chamber of the substrate.

At least a first and a second primary vacuum pump have distinct pumping characteristics.

In the example shown in FIG. 4, the first two primary vacuum pumps 13a, 13b have pumping characteristics distinct from the two primary vacuum pumps 14a, 14b.

The first primary vacuum pumps 13a, 13b have a first maximum pumping speed, for example greater than or equal to 2000m ³ / h, and the second primary vacuum pumps 14a, 14b have a second maximum pumping speed, for example less than 2000 m ^3. / h.

In addition, the difference between the first maximum pump speeds of the first primary vacuum pumps 13a, 13b and the second maximum pump speeds of the second primary vacuum pumps 14a, 14b is greater than 500 m ³ / h, such that between 500 and 3500 m ³ / h.

Claims

Pumping system intended to be connected to an enclosure (2) for loading and unloading a substrate (5), comprising at least:

a first primary pumping group (9a, 9b) having a first maximum pumping rate (SI), and

a second primary pumping group (10a, 10b) having a second maximum pumping speed (S2),

each primary pumping unit (9a, 9b, 10a, 10b) comprising a single-stage Roots vacuum pump (15) and a primary vacuum pump (13), the single-stage Roots vacuum pump (15) being connected in series and in upstream of the primary vacuum pump (13) in the direction of flow of the gases to be pumped,

said first and second primary pumping groups (9a, 9b, 10a, 10b) being connected in parallel and configured to simultaneously pump the enclosure (2) from the loading and unloading chamber of the substrate,

characterized in that said first primary pumping group (9a, 9b) has pumping characteristics distinct from said second primary pumping group (10a, 10b), the difference between the first and second maximum pumping speeds (S1, S2) ) said first and second primary pumping groups (9a, 9b, 10a, 10b) being greater than 500 m ³ / h.

Pumping system intended to be connected to a chamber (2) for loading and unloading a substrate (5), comprising at least a first primary vacuum pump (13a, 13b) having a first pumping speed. maximum and a second primary vacuum pump (14a, 14b) having a second maximum pumping rate, the first and second primary vacuum pumps (13a, 13b, 14a, 14b) being connected in parallel and configured to simultaneously pump the enclosure (2) the loading and unloading chamber of the substrate, characterized in that the first primary vacuum pump (13a, 13b) has pump characteristics distinct from the second primary vacuum pump (14a, 14b), the difference between the first and second maximum pump speeds being greater than 500 m ³ / h.

3. Pumping system according to one of the preceding claims, characterized in that the first maximum pump speed (SI) is greater than or equal to 2000m ³ / h and the second maximum pump speed (S2) is less than 2000m ³ / h. Pumping system according to one of the preceding claims, characterized in that the difference between the first maximum pump speed (SI) and the second maximum pump speed (S2) is between 500 and 3500 m ³ / h.

Pumping system according to one of the preceding claims, characterized in that it comprises at least two primary vacuum pumps (13a, 13b; 14a, 14b) or at least two primary pumping units (9a, 9b; 10a, 10b). ) having substantially identical pumping characteristics.

Process for lowering pressure in an enclosure (2) of a loading and unloading chamber by a pumping system (1) according to claim 1, characterized in that the enclosure (2) of the loading chamber is simultaneously pumped discharging the substrate by means of at least a first primary pumping group (9a, 9b) having a first maximum pumping rate (SI) and a second primary pumping group (10a, 10b) having a second maximum pumping rate (S2), said primary pumping units (9a, 9b, 10a, 10b) being connected in parallel and having distinct pumping characteristics, the difference between the first and second maximum pumping speeds being greater than 500 m ³ / h.

Method for lowering pressure in an enclosure (2) of loading and unloading chamber by a pumping system (1 ') according to claim 2, characterized in that the enclosure (2) of the loading chamber is simultaneously pumped and discharging the substrate by means of at least a first primary vacuum pump (13a, 13b) having a first maximum pump rate and a second primary vacuum pump (14a, 14b) having a second maximum pump speed, said primary vacuum pumps (13a, 13b, 14a, 14b) being connected in parallel and having distinct pumping characteristics, the difference between the first and second maximum pumping speeds being greater than 500 m ³ / h.