EP1477684B1 - Molecular,turbo-molecular or hybrid pump with intergral valve - Google Patents

Abstract

The pump has an outlet radial orifice (23) crossing a cylindrical peripheral wall (17). An integrated isolation and control valve has a coaxial annular closure unit (24) that comes in support against the wall around a radial outlet opening. The unit is axially driven by a motor (8) to place a shutter (26) opposite to the orifice for controlling an opening of the valve and regulating a flow of gas pumped by the pump. An independent claim is also included for a gas pumping system comprising a molecular, turbo-molecular, or hybrid pump.

Description

The present invention relates to gas pumping systems for establishing and regulating a suitable vacuum in a process chamber such as a chamber used in particular in the semiconductor industry.

Semiconductor fabrication processes and microelectronic mechanical systems (MEMS) generally comprise successive steps that take place in a process chamber under a low pressure atmosphere. Each process step is characterized by a gas pressure that must be regulated, for example for the maintenance of a plasma or a bombardment of particles that acts on a semiconductor substrate.

Most of the process steps are carried out in the presence of a suitable vacuum, generated and maintained by a vacuum line comprising vacuum pumps connected to the process chamber.

The vacuum line of a process chamber generally comprises a secondary pump, of molecular, turbomolecular or hybrid type, connected at the chamber outlet with the interposition of an isolation valve, and which discharges into a connecting pipe connected to the input of a primary pump whose output is discharged at atmospheric pressure. An isolation valve is usually provided at the outlet of the secondary pump.

Controlling the pressure in the process chamber requires the provision of means for modifying the pumping conditions in the vacuum line, in order to adapt them to the successive steps of the processes. In the traditional way, the pressure in the process chambers has been controlled by the operation of a control valve placed directly at the outlet of the process chamber, upstream of the secondary pump. A problem is then the risk of fouling of the control valve by the pumped gases, and the risk of retrograde pollution from the control valve to the process chamber during subsequent steps of the processes.

A solution that has been considered until now is to place the control valve in the connecting pipe, that is to say between the discharge of the secondary pump and the suction of the primary pump. The document WO 99/04325 describes in particular this solution of providing a control valve connected to the input of the primary pump not controlled in speed, while providing an injection of neutral gas upstream of the control valve.

There is then a degradation of the regulation, probably due to an elongated response time that results from the presence of a larger volume of gas at high pressure between the discharge of the secondary pump and the control valve.

The problem proposed by the present invention is both to significantly reduce the risk of clogging of the control valve and the risks of retro-diffused pollution from the control valve to the process chamber, without significantly degrading the pressure regulation conditions in the process chamber. In particular, it is necessary to guarantee a rapid reaction of the pressure regulating means during the transitions between the successive steps of the processes.

Simultaneously, the invention makes it possible to reduce the space requirement resulting from the presence of the control valve itself.

The idea underlying the invention is to integrate the control valve with the structure of the secondary pump, by providing a particular valve structure whose shutter acts directly on a radial outlet orifice in the cylindrical peripheral wall of the pump.

In practice, a secondary pump of molecular, turbomolecular or hybrid type with an output stage is provided, and the shutter acts directly on the radial outlet orifice provided in the cylindrical peripheral wall of this output stage.

In this way, the control valve is placed closer to the secondary pump, which is itself closer to the process chamber, thus reducing the reaction time upstream disturbances in the atmosphere of the process chamber .

The invention also benefits from the natural heating of the secondary pump, which heats the integrated valve and thus reduces the risk of deposition and condensation of the gases pumped on the parts of the control valve.

It is also possible to provide this control valve structure with sufficient sealing qualities to fulfill downstream valve functions. This eliminates the need for an additional downstream isolation valve.

To achieve these and other objects, the invention provides a molecular, turbomolecular or hybrid pump, comprising an output stage having a cylindrical peripheral wall and a radial output orifice passing through the cylindrical peripheral wall; the pump according to the invention further comprises a valve integrated regulating and / or isolating device having a coaxial annular obturator with passage lumen which cooperates directly with the radial outlet orifice of the output stage for sealing and / or regulating.

According to a first embodiment, the coaxial annular shutter is placed inside the cylindrical peripheral wall in an annular discharge space, bearing on the internal face of the radial outlet orifice.

According to another embodiment, the coaxial annular shutter is supported on the outer face of the radial outlet orifice, and housed around the cylindrical peripheral wall of the output stage.

The annular coaxial shutter may advantageously be biased in axial rotation by a motor to adjustably position the passage lumen relative to the radial outlet orifice. The rotation of the coaxial annular shutter displaces the passage lumen vis-à-vis the radial outlet orifice, and thus performs the control of the gas flow through the control valve and / or insulation.

In practice, the coaxial annular shutter may comprise a rack engaged with a gear wheel driven in rotation by the motor.

The motor can advantageously be housed in a casing mounted radially against the cylindrical peripheral wall of the pump, with the interposition of seals.

Preferably, the valve makes a total sealing tight in the closed position.

For this purpose, the coaxial annular shutter may comprise sealing means mounted to seal the shutter in the closed position.

According to a practical embodiment, the coaxial annular shutter may comprise a total shutter flap mounted radially on the annular coaxial shutter, and biased in radial displacement by displacement means which press against the periphery of the radial orifice of exit when it is opposite said radial outlet orifice, and that away from the cylindrical peripheral wall in its other angular positions.

To further reduce the risk of fouling of the control valve, it is advantageous to provide a nitrogen injection in an annular discharge space of the output stage.

Preferably, the nitrogen injection can be carried out inside the housing containing the drive motor of the coaxial annular shutter of the control valve, which further protects the engine itself against any risk of pollution by pumped gases.

Advantageously, the passage lumen of the coaxial annular shutter may be shaped to form a suitable conductance curve for stable and efficient control. The shape of the passage lumen defines the variation of the conductance as a function of the rotation angle of the coaxial annular shutter.

According to another aspect of the invention, there is provided a system for pumping the gases from a process chamber, comprising at least one molecular, turbomolecular or hybrid secondary pump with an output stage, and comprising at least one control valve and / or or insulation controlling the flow of pumped gases; according to the invention, the control valve and / or isolation is integrated in the output stage as defined above.

The control valve and / or isolation can advantageously be controlled by a motor and control means for performing a pressure regulation upstream of the secondary pump.

• la figure 1 est une vue schématique d'un système de pompage des gaz d'une chambre de procédés selon un mode de réalisation de la présente invention ;
• la figure 2 est une vue en perspective d'un étage Holweck de pompe moléculaire ou hybride selon un mode de réalisation de l'invention ;
• les figures 3 et 4 sont deux autres vues, à plus petite échelle, de l'étage Holweck de la figure 2, respectivement dans un état d'obturation presque totale et dans un état d'ouverture partielle ;
• la figure 5 est une vue en perspective d'un obturateur annulaire coaxial de la pompe de la figure 2 ;
• la figure 6 est une coupe diamétrale de l'étage Holweck de la figure 2, à l'état d'obturation totale ;
• la figure 7 est une coupe diamétrale de l'étage Holweck de la figure 2, dans l'état d'ouverture totale ;
• la figure 8 est une coupe diamétrale de l'étage Holweck de la figure 2, à l'état d'ouverture partielle ;
• la figure 9 est une vue de dessus de l'étage Holweck de la figure 2, dans l'état d'ouverture partielle illustré sur la figure 8 ;
• la figure 10 est une vue partielle de dessus montrant le détail du volet d'obturation totale en position d'obturation totale ; et
• la figure 11 est une vue de détail de dessus montrant le volet d'obturation totale en position de recul pour l'ouverture.

Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, with reference to the accompanying figures, in which:

• Figure 1 is a schematic view of a gas pump system of a process chamber according to an embodiment of the present invention;
• FIG. 2 is a perspective view of a molecular or hybrid pump Holweck stage according to one embodiment of the invention;
• Figures 3 and 4 are two other views, on a smaller scale, of the Holweck stage of Figure 2, respectively in a state of almost total shutter and in a partial open state;
• Figure 5 is a perspective view of a coaxial annular shutter of the pump of Figure 2;
• FIG. 6 is a diametral section of the Holweck stage of FIG. 2, in the state of total closure;
• Figure 7 is a diametral section of the Holweck stage of Figure 2, in the fully open state;
• Figure 8 is a diametral section of the Holweck stage of Figure 2, in the partial opening state;
• Figure 9 is a top view of the Holweck stage of Figure 2, in the partially open state illustrated in Figure 8;
• Figure 10 is a partial top view showing the detail of the total shutter shutter in full shutter position; and
• Figure 11 is a detail view from above showing the shutter shutter total recoil position for opening.

In the embodiment illustrated in FIG. 1, in a vacuum line for controlling the vacuum of a process chamber 1, there is provided a primary pump 2 which delivers at atmospheric pressure and whose suction is connected, by means of a connecting pipe 3, discharge 4 of a secondary pump 5 whose suction 6 is connected to the process chamber 1.

The discharge 4 of the secondary pump 5 comprises, integrated in the secondary pump 5 itself, a control valve 7 associated with means 8 for controlling the control valve 7.

As will be seen below, the control valve 7 may comprise a shutter mechanically displaceable by a motor constituting the means 8 for controlling the control valve 7. The motor 8 can be controlled by control means 9 such as a microprocessor or a microcontroller. To carry out the pressure regulation in the process chamber 1, the control means 9 can receive a setpoint signal produced by a setpoint 10, and measurement signals produced for example by a pressure sensor 11 in the process chamber 1 .

The pressure in the process chamber 1 can be controlled by the greater or smaller opening of the control valve 7, obtained by actuating the motor 8. In addition, it can be provided if necessary that the control means 9 control a power supply. 12 which controls the speed of the primary pump 2, and / or a supply 13 which controls the speed of the secondary pump 5.

A source of neutral gas 14, for example containing nitrogen, may advantageously be connected, via a pipe 15 and a control valve 16, to a housing containing the engine 8, for injecting a neutral gas which is propagated towards the inside the output stage of the secondary pump 5 through the regulating valve 7.

FIGS. 2 to 11, which illustrate an advantageous embodiment of a secondary pump 5 according to the present invention, will now be considered.

The invention applies to secondary pumps that can be of the molecular type, of the turbomolecular type or of the hybrid type.

In a molecular pump, in particular a Holweck type molecular pump, the stator comprises a cylindrical peripheral wall around an inner stator skirt from which it is separated by an annular space of discharge. A radial outlet orifice passes through the cylindrical peripheral wall and thus communicates the external atmosphere with the annular discharge space. A rotor with helical ribs is engaged coaxially in the interior space defined by the inner stator skirt and is rotated along the axis of the pump.

In a turbomolecular-type secondary pump, the rotor and the stator comprise stages of fins which fit into each other.

In a hybrid-type secondary pump, there are, starting from the suction of the pump, finned turbomolecular type compression stages followed by at least one Holweck type output stage.

In the embodiment of FIGS. 2 to 11, there is shown only the output stage of such a secondary pump 5 of molecular or hybrid type, which stage can be associated with other stages such as turbo stages.

The output stage of such a molecular or hybrid pump 5 comprises a cylindrical peripheral wall 17, a coaxial internal stator skirt 18 with helical inner ribs 19, and a Holweck rotor, not shown in the figures, which is engaged coaxially in the internal space 20 defined by the inner stator skirt 18 and which is rotated along the axis of the pump by a not shown main motor.

It will be noted that, in FIG. 2, the secondary pump 5 is seen from its downstream face, from which the downstream closure wall has been removed to make it possible to distinguish the internal members of the pump. In operation, the downstream face of the pump is closed by a disk-shaped sealed wall fixed to the cylindrical peripheral wall 17 and defining a downstream chamber 21 (see in particular FIG. 6). The pumped gases are discharged by the Holweck rotor to the downstream chamber 21 which itself communicates with an annular discharge space 22 located between the cylindrical peripheral wall 17 and the inner stator skirt 18.

The cylindrical peripheral wall 17 has a radial outlet orifice 23 through which the discharged gases escape from the annular discharge space 22.

According to the invention, there is provided a particular regulating valve structure whose closure element is directly adjacent to the radial outlet orifice 23 in the cylindrical peripheral wall 17 of the Holweck stage of the secondary pump 5.

For this purpose, the control valve comprises a coaxial annular shutter 24, of cylindrical shape, in sealing engagement against one of the faces of the radial outlet orifice 23, having a passage opening 25 (FIG. a portion of its periphery, and biased in axial rotation to adjustably position said passage lumen 25 in an angular orientation more or less aligned or offset from the radial outlet orifice 23 in order to adjust the conductance of the valve. regulation.

Such a coaxial annular shutter 24 is illustrated in isolation in perspective in a particular embodiment in FIG. 5. It can be seen in this figure that the coaxial annular shutter 24 has a cylindrical shape constituted by a continuous cylindrical wall 24a and limited by an upstream circular edge 24b and a downstream circular edge 24c. A guide groove 24d is provided on the outer wall of the wall 24a, to cooperate with guide means which fix the axial position of the cylindrical annular shutter 24 in the pump body.

The upstream circular edge 24b includes a toothed portion 24e for cooperating with a driving pinion urged by a motor for driving in axial rotation the coaxial annular shutter 24 in the pump body.

FIG. 5 also distinguishes the passage lumen 25 which, when the angular position of the coaxial annular shutter 24 faces the radial outlet orifice 23 (FIG. 6) of the pump, defines the position of total opening of the valve, and which more or less closes the control valve when it is offset away from the radial outlet orifice 23. The passage light 25 is given a shape adapted to obtain a curve of conductance suitable for achieving a stable and effective control by angular position control of the coaxial annular shutter 24 about the axis of the pump.

In FIG. 5, there is also a total shutter shutter 26, radially movable on the coaxial annular shutter 24, to be radially biased by radial displacement means which will be described later. The total shutter 26 comprises a front seal 26a to ensure complete sealing in the closed position.

In the embodiment illustrated in the figures, the coaxial annular shutter 24 is placed inside the annular discharge space 22, and is displaceable by axial rotation about the axis of the pump as illustrated by the double arrow 27 in Figure 2.

For this axial rotation movement 27, the coaxial annular shutter 24 is driven by the motor 8 placed in a casing 28 mounted radially on the cylindrical peripheral wall 17, as is best seen in FIG. 6. The motor 8 drives a wheel toothed 29 which engages on the toothed portion 24e of the upstream circular edge 24b of the annular coaxial shutter 24.

The housing 28 is radially mounted on the cylindrical peripheral wall 17 of the pump body with the interposition of a front annular seal 30. A second radial annular seal 31 is also provided in the cylindrical peripheral wall. 17 inside the passage opening of the shaft carrying the toothed wheel 29.

FIG. 6 further distinguishes the arrival of the neutral gas injection pipe 15 in the housing 28 containing the engine 8. Such an injection of neutral gas causes a flow of neutral gas through the engine 8 in the direction of the secondary pump 5, avoiding a circulation of gas pumped from the secondary pump 5 to the engine 8 to reduce the risk of pollution of the engine 8, and simultaneously ensuring a dilution of the gases in the Holweck stage, which further reduces the risks of deposit. The unidirectional flow of neutral gas is provided by providing at least one calibrated axial through hole in the toothed wheel 29.

Due to its position inside the annular discharge space 22, the coaxial annular shutter 24 takes advantage of the heating at the outlet of the Holweck stage, which reduces the risk of deposits of gas pumped on the elements of the control valve. But above all, this position of the coaxial annular shutter 24 minimizes the high pressure gas volume upstream of the control valve 7, thus improving the reaction capacity of the control.

In Figure 6, the control valve is shown in the full shutter position. In this case, the coaxial annular shutter 24 is placed in an angular position such that the total shutter 26 is exactly opposite the radial outlet orifice 23. The total shutter shutter 26 is pressed against the face internal cylindrical peripheral wall 17, around the entire periphery of the radial outlet orifice 23, and its annular seal 26a is pressed against the periphery of the radial outlet orifice 23 to ensure a perfect seal.

In FIG. 7, the secondary pump 5 is illustrated in a state in which the control valve is in the fully open position. This figure shows the elements of FIG. 6, which are identified by the same reference numerals.

In this fully open position, the coaxial annular shutter 24 has been pivoted by actuation of the motor 8 to place the passage lumen 25 in correspondence with the radial outlet orifice 23, in order to allow the maximum passage of the discharged gases. by the pump. The shutter shutter 26 is then retracted laterally, and is not shown in the figure.

In FIG. 8, the secondary pump 5 of FIG. 6 is shown in diametral section in partial open position, a position also illustrated in plan view in FIG. 9. In this case, the coaxial annular shutter 24 is pivoted. angularly by the motor to place the passage lumen 25 partially in front of the radial outlet orifice 23, which radial outlet orifice 23 is partially closed by the total shutter shutter 26. The valve is illustrated in the half position. opening.

To allow free rotation of the coaxial annular shutter 24, the total shutter shutter 26 is radially displaceable, to be spaced from the cylindrical peripheral wall 17 in all the angular positions of the coaxial annular shutter 24 except in the position of total closure shown in Figure 6.

For this, as seen in more detail in Figures 10 and 11, the total shutter 26 has an inner face 26b ramp, with a portion 26c thinner and a portion 26d thicker. The inner face 26b is supported radially on rollers 32a and 32b, clearly visible in the figures in diametral section. In total or partial opening position, illustrated in FIG. 11, the rollers such as the roll 32a bear against the thinnest part 26c of the total shutter shutter 26, allowing the total shutter shutter to retract radially. 26 in the direction of the axis of the pump, away from the cylindrical peripheral wall 17. On the other hand, in the vicinity of the total closure position, illustrated in FIG. 10, the rollers such as the roll 32a are in pressing on the thickest part 26d of the total shutter 26, pushing the shutter 26 to the outside to press against the cylindrical peripheral wall 17 around the periphery of the radial outlet orifice 23, the seal 26a then ensuring the perfect seal.

FIG. 3 illustrates in perspective the secondary pump 5 in the position of FIG. 11: the total shutter shutter 26 is slightly off-center with respect to the radial outlet orifice 23.

FIG. 4 illustrates the secondary pump 5 in the half-opening position illustrated in FIG. 8 and in FIG. 9. The total shutter shutter 26 is offset by half the width of the radial outlet orifice 23, and we also distinguish half of the passage light 25.

In the embodiment illustrated in the figures, the control valve, provided with a total shutter 26, can also provide the function of isolation valve.

It will be understood that, according to the invention, provision can be made for a simplified embodiment in which the coaxial annular shutter 24 comprises only a passage lumen 25, and is devoid of a total shutter flap 26. In this case, the valve only fulfills the function of the control valve, the complete shutter of the valve being not tight.

Also, in the embodiment illustrated in the figures, the coaxial annular shutter 24 is disposed inside the pump, and bears against the inner face of the cylindrical peripheral wall 17 around the radial outlet orifice 23.

Alternatively, the annular coaxial shutter 24 can be placed outside the cylindrical peripheral wall 17, resting on the edges of the radial outlet orifice 23.

The present invention is not limited to the embodiments that have been explicitly described, but it includes the various variants and generalizations that are within the reach of those skilled in the art.

Claims (14)

1. A molecular drag, turbomolecular, or turbo/drag hybrid pump (5) having an outlet stage with a cylindrical peripheral wall (17) and a radial outlet orifice (23) passing through the cylindrical peripheral wall (17), the pump being characterized in that it further comprises an integrated regulator and/or isolator valve having an annular coaxial closure member (24) with a through slot (25) that co-operates directly with the radial outlet orifice (23) of the outlet stage in order to perform closure and/or regulation.
2. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 1, in which the annular coaxial closure member (24) is placed inside the cylindrical peripheral wall (17) in an annular delivery space (22), the member bearing against the inside face of the radial outlet orifice (23).
3. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 1, in which the annular coaxial closure member (24) bears against the outside face of the radial outlet orifice (23), and is disposed around the cylindrical peripheral wall (17) of the outlet stage.
4. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to any one of claims 1 to 3, in which the annular coaxial closure member (24) is driven to turn about the axis of the cylinder by a motor (8) to position the through slot (25) in adjustable manner relative to the radial outlet orifice (23).
5. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 4, in which the annular coaxial closure member (24) includes a rack (24e) meshing with a gearwheel (29) rotated by the motor (8).
6. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 4 or claim 5, in which the motor (8) is housed in a housing (28) fitted radially against the cylindrical peripheral wall (17) of the pump, with sealing gaskets (30, 31) interposed between them.
7. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to any one of claims 1 to 6, in which the valve provides leaktight total closure in the closed position.
8. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 7, in which the annular coaxial closure member (24) includes sealing means (26, 26a) mounted to provide leaktight closure in the closed position.
9. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 8, in which the annular coaxial closure member (24) includes a total closure shutter (26) mounted to move radially on the annular coaxial closure member (24) and urged to move radially by displacement means (26b, 32a, 32b) which press it against the periphery of the radial outlet orifice (23) when it is in register with said radial outlet orifice (23), and which move it away from the cylindrical peripheral wall (17) in other angular positions thereof.
10. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to any one of claims 1 to 9, in which provision is further made to inject nitrogen into the annular delivery space (22) of the outlet stage.
11. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to claim 10, in which nitrogen is injected into a housing (28) containing a motor (8) for driving the annular coaxial closure member (24).
12. A molecular drag, turbomolecular, or turbo/drag hybrid pump according to any one of claims 1 to 11, in, which the through slot (25) of the annular coaxial closure member (24) is of a shape that is adapted to obtain a conductance curve that is appropriate for regulation that is stable and effective.
13. A system for pumping gas from a process chamber (1), the system comprising at least one secondary pump (5) of the molecular drag, turbomolecular, or turbo/drag hybrid type with an an outlet stage as defined in any one of claims 1 to 12, and in which the regulator and/or isolator valve controls the flow of pumped gas.
14. A gas pumping system according to claim 13, in which the regulator and/or isolator valve is controlled by a motor (8) and by control means (9) so as to regulate pressure upstream from the secondary pump (5).

Images